l^G ISULLETJN 36, UNITED STATE8 NATIONAL MUtiEUM 



LAGENORHYNCHUS OBLIQUIDENS Gill. 



L(i;/ciiorhunchus obliquidcns, Gill, Proc. Aciiil. Nat. Sci., Phihi., 1805, p. 177. 

 f Dilphiinm lotKjidenn, Cope, Proc. Aciid. Nat. Sci., Pliila., IdUB, p. ti'J5. 

 ? Clumenia lonijidens, Dall, Scammon's Mariuc Maimiialia, 1874, p. 'iS6. 

 ? Clymenia siinilis, Gray, Proc. Zool. Soc. Loudou, 18G8, p. 147. 



This species is unquestionably valid, although closely related to L. 

 acutus, Gray, and to L. crucifjer, d'Orbiguy. It would api)ear to be 

 absolutely larger than the latter, judged by the skull, aud more robust 

 though not longer than the former. The National Museum is at pres- 

 ent in possession of four adult skulls of Dr. Gill's species, and two 

 entire skeletons, representing, respectively, an adult and a rather young 

 individual. On comparing one of the adult skulls with a similar one 

 from the large series of L. acutus iu the Museum numerous differ- 

 ences become apparent. The margins of the rostrum in L. obliqui- 

 dens converge very gradually from a jioint about an inch anterior 

 to tlie notch to a point about the same distance from the tip. The 

 outline of the rostrum does not suggest a triangle, therefore, as in L. 

 acutus', but rather a rectangle, of which the anterior corners are rounded 

 off. The surface of the intermaxilloB is more convex in L. obUquidens 

 than in L. acutus, and tlie prenarial triangle is more elevated and ex- 

 tends further upon the rostrum. The orbits are much further apart in 

 L. acutus, owing to the great expansion of the proximal half of the 

 u)axill;e. Viewed from the side, the skulls of the two species are strik- 

 ingly different owing to the large size, quadrate form, and the posterior 

 and superior extension of the temporal fossa? of L. ohliquidens. The 

 biting-power of this species must be much greater than that of i. 

 acutus, not only on this account but because the teeth are larger and 

 more deeply implanted in the alveoli. In both species the roots of the 

 teeth are abruptly turned backward at their extremity, a character 

 which is common in this genus. 



The inferior surfaces of the skulls present many differences, but these 

 are difhcult to express on account of the complexity of the parts. The 

 pterygoids are the least bell-shaped in L. acutus and extend much 

 farther back than in L. obUquidens. The shape of their free margin 

 aud the extent of contact in the median line is widely different in these 

 two skulls, but this is a character which is subject to much variation. 



In proportions of parts the skulls of acutus aud obUquidens show no 

 consonance. The distance from the maxillary notch to the anterior 

 end of the temporal fossa exceeds the width of the beak at the notch 

 in acutus, but is less than the latter width in obUquidens. The breadth 

 across the proximal end of the right maxilla from the lateral free margin 

 to the superior nares equals the width of the beak at the notch in acu- 

 tus, but the former only equals three-fourths the latter in obUquidens. 

 The length of the free border of the malar only exceeds by a little more 

 thau one-half the length of tUe oibit iu obUquidens, while iu acutus the 



