92 ICHTHYOPTERYGIA. 



parietofrontal region is fairly well preserved, and agrees 

 closely with that of No. E. 1122. The almost entire in- 

 clusion of the parietal foramen in the frontals is exhibited 

 very clearly. No history. 



R. 322. A right humerus probably belonging to this form ; from the 

 Lower Lias of Lyme-Eegis. Although larger this speci- 

 men closely resembles the humerus of No. 36182, and 

 differs from that of I. tenuirostris. 



Enniskillen Collection. Purchased, 1882. 



32395. A right femur probably belonging to this species ; from the 

 Lower Lias of Lyme-Eegis. This specimen, although 

 larger, accords in contour with the femur of No. 36182, 

 and differs considerably from that of I. tenuirostris, No. 

 E. 1129. Purchased. 



c. Platyodont Subgroup. 



Teeth relatively large, and either cjlindrical and grooved, or with 

 compressed carinated crowns and the roots invested with cement. 

 Superior border of articular bone of mandible sometimes not raised 

 above the level of the alveolar border of the dentary. Centra of 

 cervical vertebra? (when known) laterally expanded, and those of 

 late posterior dorsals and anterior caudals narrowed superiorly ; 

 upper costal tubercles of a few of the anterior cervicals supported 

 partly on the arch. Coracoid (when known) with small posterior 

 notch. Humerus as in the Acutirostrine subgroup. Pectoral limb 

 in some cases not much larger than the pelvic. 



Ichthyosaurus lonchiodon, Owen 1 . 

 Cranial rostrum comparatively short and stout, and about equal 

 to three times the diameter of the orbit ; maxilla excluded from 

 narial aperture by junction of premaxilla with lachrymal ; other 

 cranial characters not apparent. Superior border of articular not 

 raised above the level of the alveolar border of the dentary. Teeth 

 cylindrical, long, and straight, with the flirtings of the crown sepa- 

 rated by a distinct smooth interval from the coarser ones of the root. 

 Neural spines of dorsal vertebrae excessively low and broad ; and the 

 centra of all the vertebrae comparatively short and with flattened 

 terminal faces. Limbs imperfectly known, but the pectoral con- 

 siderably larger than the pelvic; component bones relatively small ; 

 and the anterior border of the radiale, and (judging from the pelvic 



1 Kep. Brit. Assoc, for 1839, p. 116 (1840). 



