from the English Lower Lias. 433 



fish in the Lower Lias of Lyme Regis ; two of these speci- 

 mens being- tolerably complete, but the third wanting the 

 head and the greater part of the abdominal region, while 

 apparently shortened by accidental crushing. The principal 

 characters of the genus and species are shown in the accom- 

 panying PI. XVI. figs. 2-4. 



The maximum depth of the trunk is contained about four 

 and a half times in the total length, which does not exceed 

 0-135. The head (PI. XVI. tigs. 2, 3) is longer than deep, it 

 and the opercular apparatus together being comprised about 

 four and a half times in the total length. The orbit is large 

 and far forwards, and the snout projects somewhat in advance 

 of the mouth. The mandibular suspensorium is very oblique 

 and the jaws are slender, with a wide gape. The mandible 

 is pointed at the symphysis and bears two rows of teeth, the 

 inner series consisting of large, regular, well-spaced, conical 

 teeth, somewhat curved, and the outer series comprising nume- 

 rous closely arranged minute teeth. The dentition of the 

 upper jaw is smaller than that of the lower, though the inner 

 row is similar in character and the outer row is not clearly 

 recognizable. The cranial and facial bones are ornamented 

 with coarse rounded tuberculations, which are rarely elongated 

 and fused into short rugae ; and these tuberculations become 

 more sparse on the operculum and suboperculum. The oper- 

 culum (fig. 3, op.) is much smaller than the suboperculum, and 

 the latter element is deeper than broad. 



The vacant space occupied by the notochord is distinct in 

 the original of fig. 2, and there are no undoubted ossifications 

 in the notochordal sheath. In the abdominal region there 

 are not less than twenty-eight segments, represented by well- 

 developed neural arches and relatively minute hsemal carti- 

 lages. Each of the neural arches is robust, but elongated, 

 much expanded at its base, less expanded distally, and bearing 

 a long, slender, neural spine, which is merely apposed and 

 not in direct connexion ; the representatives of the haemal 

 arches are merely small expansions, each with a vertical 

 ridge. In the caudal region both the neural and hasmal 

 arches are complete and apparently more ossified than those 

 of the abdominal region ; the arches are all short and robust, 

 and in each case the spine is evidently directly fused with its 

 supporting pedicles. At the inferior lobe of the caudal fin 

 the ha?mal spines become expanded for the support of the 

 dermal rays, and at the base of the upper lobe there is a series 

 of interspinous bones supporting the large fulcral scales. 



All the fins are made known in the specimens under con- 

 sideration. The pectoral fins are not excessively large, and 

 Ann. & Mag. N. Hist. Ser. 6. Vol. v. 31 



