SYLL^MUS. 9] 



plate suggesting the same shape is also seen in a specimen from Burlnun in the 

 Egerton Collection (B. M. no. P. 185:]). The preoperculum (PL XXI, fig. 1, pop.) 

 is relatively enormous, triangular in shape and sharply bent at the angle, with the 

 lower limb slightly larger than its ascending limb. Its concave anterior border is 

 thickened, and the hinder expansion is marked by rounded radiating folds or 

 ridges. The number of the branchiostegal rays is uncertain ; but remains in a 

 specimen from Cuxton (B. M. no. P. 9698) seem to show at least 10 of these rays, 

 all very delicate, supported by the ceratohyal. The elongated and laterally 

 compressed ceratohyal, with its upper ends connected by a narrow bar of bone, is 

 seen in impression in the type specimen (PI. XX, fig. 1, ch.). 



The vertebras have only been satisfactorily observed in the caudal region 

 (PI. XX, fig. 2), where each centrum is about as long as deep, much constricted, 

 and strengthened by a single sharp longitudinal ridge on the middle of either side. 

 Similar centra are feebly indicated in the abdominal region of B. M. no. P. <i.V>2. 

 If they are as uniform in size throughout the trunk as in modern Clupeidoe, the 

 vertebra? must have been over 40 in total number. The neural and hasmal arches 

 in the hinder half of the tail are much thickened and overlap each other, to 

 strengthen the pedicle for wielding the powerful, forked caudal fin. 



In the pectoral girdle, the clavicle is only slightly expanded in the plane of the 

 flank above the origin of the pectoral fin ; and its inwardly directed lamina forms 

 an acute angle with this expansion, being inclined backwards to meet a well- 

 developed precoracoid arch (PI. XXI, fig. 2 a, pc). Above the pectoral fin there 

 is a long and narrow postclavicular plate (PI. XXI, fig. 2, pel.), which clearly over- 

 laps the clavicle, as usual in the Clupeidae. Its outer face is marked by numerous 

 minute pittings. The pectoral fin itself (PL XX, figs. 1, 2, pd. ; PL XXI, 

 fig. 2, pet.) is placed low down on each flank, and seems to have been received in a 

 shallow hollow when adpressed to the trunk. It must have been long and narrow in 

 shape, comprising not more than 14 rays. The pelvic fins (ph.) are extraordinarily 

 remote, arising far behind a point opposite the origin of the dorsal. Indeed, if 

 their paired nature were not distinctly shown by B. M. no. P. 6532, one of them 

 displayed singly might readily be mistaken for an anal fin. Five rays of one of 

 these fins, perhaps a little displaced backwards, are shown in PL XX, fig. 2, ph., 

 and the foremost is longest and stoutest; but more rays, probably eight in each fin, 

 are indicated in the other specimen just mentioned. The anterior part of the 

 dorsal fin is best seen in the original of PL XX, fig. 2 (do.), and in B. M. no. P. 9698, 

 where it consists of closely arranged, broad rays, of which some at least are not 

 articulated. The foremost of these rays is much the shortest, terminating in ;i 

 slender point; the second is longer but similar ; the third seems to have been the 

 longest, though it is not completely preserved. The hinder part of the dorsal tin 

 is only known by scattered fragments. There is no trace of an anal fin. The 

 caudal fin (PL XX, fig. 2, c.) is deeply forked, with slender lobes. Two or three 



