those of other limicoline birds, but are apt to be a little more complicated. In Larus argentatus, of which the tendons are represented in the annexed cut, the anterior stronger branch of the brevis tendon gives off a forwards and downwards slip to the extensors of the fore arm, from which arises the usual connection with the longus tendon. There is a second connection between the two tendons. At the origin of the t.p.b. A t.pl FIG. 171.-TENSORES PATAGII or Rhynchops (AFTER BEDDARD). patagial fan is a bony nodule, as in the petrel. The tensor longus tendon also gives off a slip (A, fig. 172) to the inside of fore arm which is also present in the auks (q.v.) In Rhynchops (fig. 171, A) there are two such tendons. Lestris antarctica, Sterna, and Larus marinus (according to FÜRBRINGER'S figure, Pl. xix.) are much the same, but are without the additional slips A and B. Of these A is present in Rissa tridactyla. The expansor secundariorum is frequently absent, but it is present in Larus argentatus, marinus, and glaucus, not in fuscus. It is absent in Sterna and Lestris; present in Anous; absent again in Rhynchops. The biceps is peculiar in some members of this family. In Larus, Sterna, and Anous the biceps has, as usual, the two heads, humeral and coracoidal; but they form two perfectly distinct muscles, of which one, the coracoidal, soon divides into two distinct muscles again, which are inserted FIG. 172.-TENSORES PATAGII OF Larus argentatus (AFTER BEDDARD n, osseous nodule. Other letters as in fig. 171. respectively upon the radius and ulna. The biceps head goes to the radius, and as a rule gives off the biceps slip to the patagium; but in Larus ridibundus, according to FÜRBRINGER, this slip arises from the coracoids, an anomaly observable also in the petrel, Thalassiarche. Rhynchops has no biceps slip at all. The anconaus is generally attached by a tendon to the humerus. A A The cæca vary considerably in their development, as the following table of measurements shows: The lobes of the liver are subequal in Sterna, Anous, Gygis, and Rissa. In Larus and Lestris the right is the larger. A gall bladder is always present. In Anous the caca are quite short; in Gygis long and charadriine. The syrinx of this family is typically tracheo-bronchial (at any rate in Larus), with well-developed muscles, which always reach the bronchi. The family thus differs from other Limicolæ where there is a tendency towards a retrogression of the intrinsic muscles, sometimes culminating in actual disappearance. In Larus marinus the last six or seven tracheal rings. are rather narrower from above downwards than those which precede them, and are more or less firmly attached (except the last ring, which is incomplete both in front and behind) to form a box. When the syrinx is viewed from behind, a broad three-way piece is seen, into the formation of which the penultimate tracheal ring and the four or five in front of it appear to enter. This piece, however, is only really solid at the edges, the bars being a continuation of the penultimate tracheal rings. In the middle it is so thin as to be little more than a membrane. The first bronchial semi-ring (to which the intrinsic muscles are attached) is bow-shaped and in close contact with the last tracheal ring. The remaining semi-rings are narrower and run in a straight direction across the bronchi. The membrana tympaniformis is distinguished by its thinness and transparency from the thick yellowish membrane which unites the edges of the greater number of the bronchial semi-rings. In Larus fuscus and L. glaucus the differences are but slight, and chiefly concern the greater solidity of the threeway piece. In Larus argentatus the edges of the three-way piece are most solid; but they are connected by a series of four or five bars which divide up the central region of the threeway piece into alternate thicker and thinner portions. This is a peculiar specialisation of the three-way piece which I have not observed elsewhere. There is, furthermore, a thin bony curved rod, closely applied to the outside of the threeway piece, which arises from, or is at least connected with, the last tracheal ring. Lestris antarcticus has a syrinx which is rather different from that of Larus, and which points in the direction of the Charadriidæ, owing to the fact that the intrinsic muscles do not reach the bronchial semi-ring except as a fibrous band. The three-way piece, which is solid, is formed by two or three tracheal rings; there is no differentiation in membrane closing bronchial semi-rings. It is evident from the foregoing account that, while there are a few differences between the various genera of Laridæ, Rhynchops is quite the most anomalous form in structure as well as in external appearance, as seen in its remarkable bill, with its scissor-like edge and projecting mandible. Still, the differences are, in my opinion, not sufficient to place Rhynchops in a family by itself opposite to the remaining Laridæ. It seems that the usually received division of the family, making an additional one for Rhynchops, will serve to divide naturally the Laridae; we may term these divisions. subfamilies. They will be thus characterised : Subfamily I. Larinæ. Muscle formula of the leg, AXY+. Caca rudimentary. Biceps slips and expansor secundariorum present. Subfamily II. Stercorariinæ. Muscular formula, AXY+. Caca long. Biceps slip present. Expansor secundariorum absent. Subfamily III. Sterninæ. Muscular formula, ABXY+. Cæca rudimentary. Biceps slip present. Expansor secundariorum absent. Subfamily IV. Rhynchopinæ. Muscular formula, ABXY-. Cæca rudimentary. Biceps slip and expansor secundariorum absent. Gygis and Anous require further investigation before they can be placed in this system; they are usually regarded as terns by HOWARD SAUNDERS, for example. Anous has the complete muscle formula. Gygis has the formula of the gulls; but then the tern, Sternula (sp.), wants the accessory femoro-caudal, and in this approaches the gulls. Anous has the expansor secundariorum. Of undoubted or reputed extinct limicolous birds a number have been described. If Paleotringa (with three species), from North America, is rightly referred by MARSH to this group, it goes back to Cretaceous times. Milnea, from French Miocene, is known by the humerus. Elorius, known by an imperfect coracoid, a tarsometatarsus, and parts of the skull, seems to belong here. Egialornis is considered by LYDEKKER to have been a gull-like bird, largely on account of the perforated first phalanx of the second digit. Halcyornis has been described from the extremity of a humerus and the back of the skull. A character which we have seen (supra, p. 351, footnote) to be of no account in fixing affinities. Nostrils Basipt. Pr. Occipital Muscle Formula of Leg |