DERCETIDJS. 
183 
P. 9170. Remains of very small contorted fish exhibiting eight 
rays in one of the pelvic fins ; Sahel Alma. Lewis Coll. 
47359. Imperfect trunk with anal fin ; Sahel Alma. Lewis Coll. 
48088. Imperfect trunk with dorsal fin, associated with Bhmellus 
furcatus ; Sahel Alma. Lewis Coll. 
46533, - a. Two examples of caudal region, the second displaying 
more than 30 rays in the dorsal fin ; Sahel Alma. 
Lewis Coll. 
P. 1902. Hinder portion of fish, showing seven rays in the pelvic, 
and eight or nine in the anal fin ; Sahel Alma. 
Egerton Coll. 
The following specimens may represent unusually large in- 
dividuals of Leptotrachelus gracilis, but are too imperfect for 
satisfactory determination : — 
P. 4852. Imperfect anterior portion of fish, noticed and the head 
figured by Davis (Trans. Roy. Dublin Soc. [2] vol. iii. 
1887, p. 622, pi. xxxviii. fig. 2) under the name of 
Leptotrachelus triqueter, var. re; Sahel Alma. The head 
is shown in lateral aspect, much fractured, with some of 
the slender clustered teeth exposed ; while fragments 
of the external hones in the hinder portion of the 
cranial roof and in the mandible are ornamented with 
very fine tubercles. These tubercles on the dentary and 
angular hones are arranged in obliquely-directed, nearly 
parallel lines. The opercular apparatus is evidently 
well-developed, though the separate elements cannot be 
distinguished. The vertebral centra are similar in pro- 
portions to those of L. gracilis, and show some of tho 
expanded transverse processes supporting remarkably 
slender ribs. Above the vertebral column there are 
longitudinally extended rods stouter than the ribB, which 
seem to be intermuscular bones. Above the vertebrae at 
the hinder end of the fossil may also be observed the 
narrow heart-shaped scutes of the flank, which are 
ornamented with radiating lines of fine tubercles. The 
dorsal and ventral borders, with their scutes, are broken 
away. Lewis Coll. 
P- 4019. Hinder half of equally largo fish; Sahel Alma. The 
characteristic vertebrae are imperfectly shown, and there 
are remains of the pelvic, anal, and caudal fins. The 
