LIASSIC FORMATIONS. 113 



of Barrow-on-Soar ; it occurs, likewise, in the same formation at Stratford-on-Avon. 

 In all these localities Ammonites of the species Arietites Bucklandi have been associated 

 with the Ichthyosaurian fossils. 



c. Ichthyosaurus intermedius, Cb. (Plate XXIV. fig. 7, PI. XXX, figs. 1 and 2). 



In this species the orbits are of moderate size, 1 and the facial portion of the skull in 

 advance equals in length about three times the antero-posterior diameter of the orbital 

 outlet. The teeth (Plate XXIV, fig. 7) are relatively smaller and longer than in Ich. com- 

 munis (ib., figs. 5, 5') ; the crown has a narrower base, is more acutely conical, with finer 

 longitudinal striae, and the root has less prominent ridges. The number of teeth is from 

 thirty-five to forty on each side of both upper and lower jaws. 



The entire length of the skeleton is from five to five and a half times that of the 

 mandible. 



In the best preserved specimens the number of vertebrae ranges between 130 and 

 140. In the space between the scapula and pelvic arches there are about forty vertebrae, 

 which may be termed ' abdominal.' The neural spines increase in length and fore-and- 

 aft diameter to beyond the middle of this region, and, by reason of their antero-posterior 

 breadth, they are in contact with each other. The fin-bend of the tail occurs at about 

 the seventy-sixth or eightieth vertebra. 



The di- and par-apophyses become confluent at or about the forty-sixth vertebra, and 

 such single ' transverse process,' or tubercle, disappears near the tail-bend. 



The ribs are slender, and become flattened and longitudinally grooved along their 

 distal halves. After the fortieth pair, or thereabouts, they become straight, short, 

 rounded, without the groove, and resemble mere ' transverse processes/ 



Three neural arches in the subject of fig. 1, PI. XXX, have been dislocated near the 

 bend of the tail. In these, the neurapophyses are short and confluent, with a trans- 

 versely broad, quadrate neural spine (Cut, fig. 5), the quadrature being due to an abrupt 

 truncation of the spine. 



Fig. 5. Fig. G. 



Neural arch, front view. Caudal vertebra, side view. 



Nat. size. Nat. size. 



1 Compare with fig. 3, pi. XXVIII, Ichthyosaurus longirostris. 



