DERCETIDjE. 
179 
arm of three successive ventral scutes. Moreover, a few 
of tho dorsal scutes here appear to have their postero- 
inferiorly inclined arm extended in like manner. 
Lewis Coll. 
P. 4018. Another fine specimen, showing the Hank-scutes of the 
anterior abdominal region ; Sahel Alma. Lewis Coll. 
49537. Imperfect contorted fish, with reflexod head; Sahel Alma. 
Immediately in front and behind the orbit there are 
remains of a delicate plate, which may belong to the 
cheek. Clustered slender conical teeth are observed in 
the jaws. Some of the anterior vertebra: exhibit the 
characteristic laminar transverse processes, while a few of 
the caudals still bear the short neural spine. The large 
pelvic fins are crushed together in the usual situation. 
The dorsal fin is evidently similar to that of no. 49536, 
but the rays are depressed and cannot be counted ; some 
of its supports are distinct in the hindor part, each much 
expanded at the articulation with the corresponding raj'. 
Immediately before and behind the dorsal fin the double 
series of dorsal scutes is preserved, thoso of both sides 
being exposed from the inner aspect ; it is also clear that 
this double series was continuous along the base of the 
fin. A few of the ventral scutes are shown from the 
external aspect, with spine broken away, in the hinder 
part of the caudal region ; and those of the left side are 
exposed in continuous series above the base of the anal fin. 
The caudal fin is expanded by crushing. Lewis Coll. 
I s - 4863. Nearly complete fish bent in the middle and with 
imperfect fins ; Sahel Alma. In the abdominal region 
the very slender ribs are shown suspended from the 
expanded transverso processes ; and there are traces of 
the delicate laminar pelvic fin-supports. Here may also 
be distinguished some of the narrow heart-shaped flank- 
scutes, becoming more markedly triradiate near the origin 
of the dorsal fin ; while between this row and those on 
the ridge of the back there is a double series of relatively 
small and delicate triradiate scutes. Lewis Coll. 
49535. Imperfect head and abdominal region, lateral aspect ; 
Sahel Alma. One small autorbital cheek-plate is observed 
on the head, and there seems to be a more fragmentary 
postorbital ; there is also a cluster of slender conical 
n 2 
