660 ME. A. SMITH WOODWABD ON THE S0-0A1,1BD [NoV. 20, 



teeth, laterally compressed but without trenchant edges. There is 

 also a pair of still larger teeth of a similar character immediately 

 within the symphysis of the mandible. All the teeth are smooth. 

 The preoperculiim (fig. 1, p.op.) is relatively thin, broad at its 

 angle, and marked with radiating sensory canals. The limits of 

 the operculum and suhopcrculum are not quite clear ; and of the 

 hranchiostegal rays it can only be said that they are numerous, 

 perhaps about 20 on each side. A gular plate may or may not 

 have been present, but no remains of it are preserved. 



The centra of the anterior abdominal vertebrae are deeper than 

 long, and strengthened by peripheral secondary calcifications in 

 the form of irregular lougitudmal ridges. The scales are large and 

 smooth. 



As shown by the characters of its dentition, the fossil thus 

 described evidently pertains to a genus distinct from that to which 

 Osmeroides lewesiensis is referred. In the absence of the trunk, 

 however, it is difficult to determine its precise position ; and it can 

 only be said to approach most nearly the ElojJS-^ke fishes from 

 the Chalk of Bohemia and Dalmatia to which the generic name 

 Elopopsis has been applied. It agrees with these especially in the 

 nature of the dentition, the form of the mandible, and the 

 characters of the preoperculum. As a temporary expedient, the 

 Brighton fossil may therefore bear the name of Elopopsis crassus. 



3. AuLoiEPis TYPUS. (Plate XLIII. figs. 2-6.) 



Aulolepis typus, L. Agassiz, Poiss. Toss. vol. v. pt. i. p. 14, pt. ii. 



p. 109, pi. Ix.a. figs. 5-8 (1834-44) ; A. S. Woodward, Proc. Geol. 



Assoc, vol. X. p. 324 (1888). 



Another generic type from the English Chalk commonly regarded 

 as a Salmonoid is named Aulolepis. Only a single species, A. typus, 

 is known ; but this is represented by so large a series of specimens 

 in the British Museum that it makes an important contribution 

 to our knowledge of the osteology of the Cretaceous physosto- 

 niatous fishes. 



The head is known almost exclusively by the external bones. 

 The cranial roof (fig. 2) is flattened mesially, but somewhat arched 

 downwards at the lateral margin; and the occipital border is 

 either straight or with a slightly re-entering angle. The supra- 

 occipital exhibits a median vertical keel on its hinder face, but the 

 bone is almost or quite excluded from the superior aspect of the 

 skull. The jmrietals (pa.) meet in an irregular wavy suture, as also 

 does the hinder portion of thefrontals (/>.), and the former bones 

 scarcely attain one-third of the length of the latter ; the transverse 

 suture between these two pairs of elements is likewise unsymmetri- 

 cally wavy. The squamosals (sq.) are as broad as the parietals, but 

 extend further forwards on the outer margin in a narrow process. 

 Each frontal (fig. 3) is very broad behind and much tapering in 

 front, while the longitudinal sensory canal opens on its surface in 

 a series of srnall pores. The ethmoidal region of the cranium can 

 only be described as narrow, not much expanded at the extremity. 



