ESPECIALLY MYCTOPHOIDS 57 
curving only slightly towards the ventral region. Thus an elongated, extremely 
thin ‘ neck ’ region is produced, only appearing to widen near the dorsal and pelvic 
fins. The region below the vertebral column was presumably occupied by a highly 
distensible stomach region. Intermuscular bones, both epineurals and epipleurals, 
are present along much of the body. 
Median fins and tail. The median fins are shown in the restoration, Text-figure 
23. The dorsal fin is elongate and composed of approximately 35 rays, occupying 
the mid-third of the trunk. Anteriorly the fin rays are well formed, segmented and 
branched, the more posterior fin rays are small and feeble but still branched and 
segmented. The proximal radials have a short shaft region with an expanded 
stellate head for the articulation of the fin rays. 
The anal fin is small and remote, occurring well behind the dorsal fin and quite 
close to the caudal fin. Eight or 9 small rays are visible, all branched and segmented. 
The caudal skeleton appears to consist of at least 3 free preural vertebrae with a 
distinct free ural vertebra (ural 1) and possibly a terminal half-centrum representing 
the remains of ural vertebra 2. Apart from these facts practically nothing can be made 
of the caudal skeleton. The fin itself consists of 19 principal caudal rays of which 17 
are branched. Accessory fin rays above and below the caudal fin number about 12. 
Scales. The body is devoid of normal squamation but there are 3 rows of enlarged 
basically triradiate scutes (Text-fig. 82A) along each flank. The two major rows of 
scutes positioned dorso-laterally and ventro-laterally are triradiate. Each scute 
has an elongated anterior extension and two divergent posterior extensions ; the 
angle between the posterior arms is about 60°. The scales on the dorso-lateral part 
of the flank have a longer upper posterior arm which curves over on to the dorsal 
surface of the body approaching its fellow of the opposite side. Similarly in the 
ventro-lateral row the lower posterior arm is the longer and it too curves round 
towards the ventral surface. Intermediate, lath-shaped scutes occur in two distinct 
rows on the caudal region of the body, as extensions towards the mid-line of the 
flank from the shorter posterior arms of the major scutes. The third row of scutes 
which occurs along the whole length of the body is positioned on the course of the 
lateral line. These scutes are smaller, markedly less triradiate, elongate and heart- 
shaped. All of the scutes in the three major rows bear a small backwardly projecting 
spine arising from the angle between the two posterior arms. These spines are more 
pronounced and uncinate in the caudal region. 
A great variability in the shape of the scutes occurs within the genus Dercetis and 
even within the species Dercetis triqueter, the nature of the scutes appearing to be 
dependent on the size of the specimen. Thus in the larger specimens the triradiate 
nature of the scales becomes obscured due to the expansion of the scale between each 
pair of arms. This expansion of the scales imparts an almost complete covering to 
the flank, the three major rows now practically contacting each other. 
REMARKS. Two further species of Dercetis occur in the Sahel Alma deposits, 
Dercetis gracilis (Davis) (Text-figure 25) and Dercetis rostralis (Signeux) (Text-figure 
26). The former is generally more fragile and smaller in size than the latter and the 
