inal manuscripts of Lalande, at the request of Leverrier. He had found that the doubtful marks of the printed copy were not contained in the original record; and that there was an observation of the planet of May 8, 1795, which was not published. More than fifty years ago, then, Lalande had in his possession observations enough of Neptune to have discovered it; and he could not have failed to make this discovery if he had taken reasonable pains to satisfy himself as to the discrepant character of the observations by a new comparison with the

stars.

Professor Peirce stated that he had compared the observation of May 8, 1795, with Mr. Walker's orbit, and found it to be perfectly consistent with the slight changes which are required to satisfy the observation of May 10, 1795. Mr. Walker's orbit cannot, therefore, differ much from the exact orbit, and there can be no important error in adopting it as the basis of further research. The period is very near the double period of Uranus, but yet it seems to differ too much from this double period to admit of the establishment of a libration about that period. The principal effect of Neptune upon Uranus must, in case of the failure of this double period, be exhibited in the manifestation of an equation of the centre different from that which belongs to the proper elliptic motion, so that Uranus will have two equations of the centre, one of which will belong to its ellipse, and the other to the attraction of Neptune.

James D. Dana, Esq., Corresponding Member of the Academy, presented (through the Corresponding Secretary) a paper comprising brief characters of the Crustacea collected in the United States Exploring Expedition under Captain Wilkes, as follows:

Conspectus Crustaceorum, in orbis terrarum circumnavigatione, C. Wilkes e classe Reipublicæ Fœderatæ duce, collectorum auctore J. D. DANA.*

Conspectus narrationis uberioris auctore auctoritate publicâ edendæ.

Pars I.-CRUSTACEA COPEPODA (CYCLOPACEA*).

Familia I. CYCLOPIDE.

Oculi duo simplices tantum. Palpi mandibulorum maxillarumque breves aut obsoleti. Sacculi ovigeri duo.

Genus I. CYCLOPS.

Antennæ maris antica subcheliformes aut articulo geniculante instructæ.

1. CYCLOPS BRASILIENSIS.-C. cephalo-thorace posticè obtuso, abdominem longitudine superante; antennis anticis in utroque sexu elongatis (cephalo-thorace longioribus), articulis primo secundoque majoribus et setis oblongis apice instructis, setis antennarum aliis brevibus; anntennis maris 7-articulatis, articulis tribus basalibus crassissimis, reliquis teretibus, femina, 14-articulatis, teretibus; stylis caudalibus

Cyclopaceorum organa sunt: Cephalo-thorax 4-7-articulatus.

tectum.

Abdomen 1-6-articulatum, carapace non

Frons sæpissimè rostrata, rostro aut simplice, aut furcato, aut transversim emarginato, aut appendicibus instructo.

Oculi duo simplices, pigmento aut connati aut disjuncti; quoque quibusdam, oculi duo coaliti sub capite insistentes; aliis, oculi lenticulis duobus grandibus, uno oblato, uno prolato, constructi.

Antennæ antica 4-28-articulatæ, aut simplices, aut appendiculatæ; posticæ, 2-5-articulatæ et sæpe ramum ferentes, aliis apice setigeræ, aliis subcheliformes. Mandibule apice dentatæ, sæpius palpigeræ.

Maxillæ duæ setosæ; sæpe palpigeræ, palpo sive parvulo et vix discernendo, sive setas diffusas ferente

Maxillipedes duo, aliis parvi et parcius setigeri, aliis crassiores et valde setigeri, setis spinulosis.

Pedes antici duo simplices, aut obsolescentes, aut elongati, aliis setigeri setis non spinulosis, aliis subcheliformes.

Pedes biremes decem; octo anteriores sæpius natatorii, sed duo antici interdum subprehensiles; duo posteriores plurimum obsoleti aut parvuli; in quibusdam masculinis pergrandes et uno ambove prehensiles.

Abdomini pertinentes ad basin sæpissimè pedes spurii, sive obsolescentes, sive oblongi et setis armati; ad extremum, styli caudales duo, unusquisque 4-6 setis plerumque plumosis instructus.

Ad segmentum cephalo-thoracis septem-articulati primum, antennæ quatuor pertinent; ad secundum, mandibula, maxillæ, et maxillipedes; ad tertium, pedes quatuor antici; (cephalo-thorace quadri-articulato, hæc tota ad segmentum anticum pertinent ;) ad segmenta sequentia, singulatim, duo pedes biremes.

oblongis, tres articulos abdominis ultimos simul sumtos fere æquantibus, setâ secundâ fere abdominis longitudine, primâ dimidio breviore. Hab. Rio Janeiro.

2. CYCLOPS CURTICAUDUS.-C. femina cephalo-thorace posticè obtuso, abdominem longitudine valde superante; antennis anticis dimidio cephalo-thorace valde longioribus, 13-14-articulatis, articulis brevibus, quinque basalibus non oblongis; setis antennarum † inæqualibus, posterioribus articulorum penultimi et præantepenultimi longioribus (quatuor articulos ultimos simul sumtos longitudine æquantibus), anterioribus perbrevibus; stylis caudalibus prælongis, dimidio abdomine vix brevioribus, setis curtis, secundâ tertiâque subæquis et stylo paulo longioribus.

Long. ".- Hab. Valparaiso, Chile.

3. CYCLOPS PUBESCENS.-C. cephalo-thorace pubescente, abdominem longitudine vix superante, posticè subacuto; antennis anticis feminæ dimidii cephalo-thoracis longitudine, 8-9-articulatis, setis totis brevibus; antennis maris brevioribus, tribus articulis basalibus curtis, quarto crassissimo subovato, dimidii antennæ longitudine, ultimo (forsan duplice) tenui brevique, digitiformi; stylis caudalibus abdomine quadruplo brevioribus, setâ secundâ abdomine longiore, primâ brevissimâ. Long.

".- Hab. Valparaiso, Chile.

4. CYCLOPS MACLEAYI.-C. femina cephalo-thorace abdomine valde longiore; antennis anticis longis (cephalo-thoracem æquantibus), ad basin paulo crassioribus, articulo secundo oblongo, 5-6 sequentes brevissimos simul sumtos longitudine fere æquante, 10 reliquis paulum oblongis, septimo longiore, setis articuli secundi et septimi parum elongatis, duorum subultimorum† totis brevibus, ultimi articulum longitudine vix superantibus; stylis caudalibus tenuibus, duos articulos abdominis longitudine æquantibus, setâ secundâ abdomine breviore, primâ fere styli longitudine.

Long.". Hab. in vicin. Sydney, N. S. W.

* Setarum caudalium interior est nobis prima, et sequentes ordine, secunda, tertia, et cet.

Setæ antennarum plerumque valent ad species distinguendum, et præcipuè illæ articulorum ultimorum. Articulos 2, 3, aut 4, ultimum præcedentes, subultimos sæpe vocamus; et eorum setæ, anteriores et posteriores, scrutandæ et comparandæ.

5. CYCLOPS VITIENSIS.-C. feminæ cephalo-thorace posticè fere obtuso, abdominem longitudine vix superante, nudo; antennis anticis longis, cephalo-thoracis longitudine, multi-articulatis, articulo primo crasso, oblongo, secundo dimidio minore, 6 sequentibus perbrevibus; setis antennarum inæqualibus, articulorum primi secundique paulo longioribus, ultimi et 3 subultimorum posterioribus subæqualibus, articulo suoque paulo longioribus, setis anterioribus subultimorum perbrevibus; stylis oblongis, vix duorum articulorum abdominis longitudine, setâ secundâ abdomine paulo longiore.

Long.". Hab. in Venua Lebu, ad Insulas Viti.

Oculi duo simplices tantum. Palpi mandibulorum maxillarumque parvuli, aut obsoleti, setis diffusis non instructi. Sacculus ovigerus unicus. Antennæ postica setis habitu digitorum apice instructæ.

Genus I. HARPACTICUS. Milne Edwards.

Frons subrostrata, appendicibus nullis. Antenna antica maris subcheliformes, aut articulo geniculante instructa; feminæ basi 2-5 articulatâ et quasi curto flagello sæpius minutè 5-articulato compositæ, apice basis appendicem brevem ferentes. Cephalo-thorax 4-articulatus. Pedes antici subcheliformes mediocres.

SYN. Arpacticus, et Cyclopsina partim (C. castor, excluso), M. Edwards. Nauplius, Philippi. - Canthocarpus, Westwood. - Doris, Koch. Canthocarpus et Arpacticus, non Cyclopsina, Baird.

1. HARPACTICUS VIRESCENS. - H. cephalo-thorace ovato, anticè rotundato et breviter rostrato, segmentis posticè non acutis, abdomine paululum subito angustiore et posticè sensim decrescente, 5-articulato; antennis anticis brevibus, dimidii cephalo-thoracis longitudine, 9-articulatis, articulis basalibus quatuor, crassiusculis, secundo maximo, setis perbrevibus; pedibus anticis parvis, digito dimidii articuli secundi longitudine; stylis caudalibus brevissimis, paulum divaricatis, setâ secundâ corporis longitudine, primâ tertiâque subæquis abdomine valde brevioribus.

Long.". Hab. Madeira, in litora insulæ.

2. HARPACTICUS CONCINNUS.-H. feminæ cephalo-thorace longè ovato, segmentis posticè acutis; abdomine subito paulum angustiore, lato, lateribus bene recto, 6-articulato, parce decrescente, articulo

primo brevissimo; antennis anticis brevibus, 9-articulatis, articulis basalibus quatuor, attenuatis, setis brevibus, apice paulum longis (flagellum longitudine æquantibus); pedibus anticis parvis, articulo secundo infra obtuso-angulato et digitum longitudine duplo superante; stylis caudalibus brevissimis, parum divaricatis, setâ secundâ corpore paulum breviore, tertiâ fere dimidio minore, reliquis brevissimis.

Long.". Hab. in mare Pacifico prope Valparaiso.

3. HARPACTICUS SACER. - H. cephalo-thorace ovato, anticè subdeltoideo, segmentis posticè obtuso, dimidio longitudine latiore; abdomine subito multo angustiore, et breviore quam cephalo-thorax, 6-articulato, articulo primo brevi; antennis anticis brevibus, feminæ 9-articulatis, articulis basalibus quatuor, setis totis brevibus, maris articulo quinto (6?) crassissimo, subovato, margine anteriore subrecto, digito 2-articulato duabus setis minutis ad apicem instructo; pedibus anticis parvis digito tenui, largè dimidii articuli secundi longitudine; stylis caudalibus brevissimis, parum divaricatis, setâ secundâ corporis longitudine, tertiâ dimidio breviore, primâ perbrevi.

Long.". Hab. in litora ad Valparaiso.

4. HARPACTICUS LINEARIS. H. corpore fere lineari, abdomine non angustiore, posticè parum attenuato; antennis anticis brevissimis, 7-articulatis, articulis basalibus duobus crassissimis, primo majore, secundo perbrevi, setis totis brevibus; stylis caudæ styliformibus, articulo abdominis ultimo longioribus, parum divaricatis, setâ secundâ longitudine fere dimidii corporis.

5. HARPACTICUS ROSEUS.- H. corpore fere lineari, abdomine non angustiore, antennis perbrevibus et tenuissimis, basi non crassioribus, setis totis brevibus; stylis caudalibus brevibus, non divaricatis, setâ secundâ corpore longiore, spinulosâ.

Long.". Hab. in mari Sulu.

6. HARPACTICUS ACUTIFRONS.-H. maris cephalo-thorace angustè elliptico, anticè acuto, posticè obtuso; abdomine subito angustiore, 6-articulato, posticè valde attenuato, articulo ultimo angustissimo; antennis anticis brevibus, 3 articulis basalibus non oblongis, tertio minimo, quarto crassissimo et cylindrico prope dimidii antennæ longitudine, quinto (forsan duplice), digitiformi, parvulo; antennis juxta basin et ad apicem breviter setigeris; stylis caudalibus minutis non divaricatis, setâ dimidio corporis parum longiore, strictè appressâ, nudâ.

Long.". Hab. in mari prope Tierra del Fuego.