1907.] OF THE SUBORDER ALL0TRI0C4NATHI. 637 



The mesethmoid is entirely posterior to the prpefrontals. In 

 front of the mesethmoid the cartilaginous floor of the anterior 

 cranial chamber bears a median keel, corresponding to the keel of 

 the vomer in Lmnpris. In Velifer, however, the vomer does not 

 ossify thi'ough, bnt only sends up a pair of wings which flank the 

 praiethmoid cartilage. 



The mouth (text-fig. 170, p. 640) is more protractile than in 

 Lampris, but the prgemaxillaries and maxillaries are arranged on 

 the same plan. The hyo-palatine, orbital, and opercular bones 

 are as in Lanvpris. 



The vertebial column comprises 33 vertebrae, 16 pi-ajcaudals and 

 1 7 caudals ; the ribs are attached to downwardly directed para- 

 pophyses ; the first centrum is short and is convex anteriorly. 



The pectoral arch difiers from that of Lampris in that the 

 coracoid is normal and the pterygials are 4 in number, the last 

 in contact with the coracoid. As in Lampris the post-clavicle is 

 simple and elongate. 



The pelvic bones are a pair of erect subti-iangular plates, with 

 their apices imbedded in the ligamentous tissue between the 

 coracoids. 



Trachypterid(x. 



The skeleton of Trachypterus tcenia is feebly ossified, and the 

 bones are very thin and light, almost papery. There is no 

 occipital crest, and the epiotics meet behind the supi-aoccipital, 

 but in all other essentials the cranium (text-fig. 168) agrees with 

 that of Velifer. 



Text-fig. 168. 



prd 



' ps. 



Cranium of Tracliypterns tcenia. 

 Lettering as in test-fig. 166. 6s., basisphenoicl. 



Of the orbital bones only the prfeorbital is ossified. The 

 maxillary and prsemaxillary (text-fig. 169, p. 639) are on the 

 same plan as in Velifer., but the former bone has the outer blade 

 expanded and closely attached to the pra?maxillary 



