118 FOSSIL REPTILIA OF THE 



platyodon ; the neural arch and spine have a less vertical, in proportion to the fore-and-aft, 

 extent (PI. XXXI, fig. 6) than in Ich. communis or in Ic/i. tenuirostris. Forty-five of 

 these vertebrae may be counted between the occiput and the pelvis; and as many 

 beyond may be made out in the subject of fig. 4, PI. XXXI, as brings the number up to 

 120, but the tail is incomplete. 



The length of the rostrum anterior to the orbit (PI. XXXI, fig. 5) includes little 

 more than three longitudinal diameters of that cavity ; it is thus relatively shorter than 

 in Ich. platyodon, and it is relatively more slender than in Ich. intermedius. The mandible, 

 however, does not partake of this proportion, but is nearly as deep and strong, rela- 

 tively, as in Ich. platyodon (ib., fig. 2). The surangular (30) extends farther forward 

 than the angular (31) ; both disappear in the usual pointed form. The nostril is divided 

 from the maxillary by union of the premaxillary with the lacrymal. The pair of hyoid 

 elements (cerato-hyals) are preserved in situ in the subject of fig. 5 ; they are cylindrical, 

 almost straight, truncate at each end, which very slightly exceeds in thickness the rest of 

 the bone. Each is about one fifth the length of the mandibular ramus. 



The coracoid (PI. XXXI, fig. 7) shows a deep anterior notch, with only a feeble 

 concave outline at the corresponding part of the hind border of this bone. The clavicle 

 is applied and suturally attached to the lower half of the fore border of the scapula. 

 That border is nearly straight ; the hinder one is concave through the backward pro- 

 duction of the thickened lower end to contribute to the articular surface for the humerus. 

 The anterior border of the radius and succeeding ossicle is emarginate. The chief 

 phalanges of but three digits are preserved in the subject of PI. XXXI, fig. 4. The 

 character of the pectoral fin of the present species is probably rightly indicated in the 

 main; and in such essentially tridactyle character Ichthyosaurus lonchiodon may agree 

 with Ich. platyodon. 



The lower or distal ends of ischium and pubis seem to be equally expanded ; both 

 bones are broader than the ilium. The ventral fin has been dislocated and bent back- 

 ward close to the spine. The homotypal ossicles show the same emargination as in the 

 pectoral fin. 



This species has hitherto been found only at Lyme Regis ; it appears to be a rarer 

 Liassic Ichthyosaur than the three preceding ones. The skeleton above described was 

 discovered by Miss Mary Anning, to whom the discovery and extrication of many rare 

 and interesting fossils of the Lias of this locality are due. 



/. Ichthyosaurus longifrons, Ow. PI. XXIII, figs. 1 — 5 ; PI. XXIV, fig. 1 ; PI. XXV, 



fig. 1 ; PI. XXVI, fig. 1 ; PI. XXVII, figs. 2—5. 



The characters of this species are those in which the subjects of the above plates and 



