98 PISCES. 



separate and not anchylosed with the neural spine. The pectoral arch 

 comprises two pairs of membrane-bones, clavicles and supraclavicles, and 

 the latter are very firmly articulated with the post-temporals, which are 

 shaped as in Amia. The basal bones of the pectoral fin are large and 

 much elongated, more than five in number ; the pelvic fin-supports are 

 unknown. The fulcra on all the fins are biserial. The chain of supra- 

 temporal plates is variable, but usually consists of more than one pair. 

 There is a series of postclavicular scales, two of these being much 

 enlarged ; and there are also three enlarged scales round the anus, 

 which seems to have been mesially placed just in front of the anal 

 fin. Nearly all the other scales are in regular series, and those of the 

 flank are united by a feeble peg-and-socket articulation ; a single row 

 of scales, however, at the base of the dorsal, anal, and caudal fins 

 does not conform to the regular flank series, but is directly related to 

 the fin-rays and fulcra. The course of the sensory canals on the trunk 

 can be traced by perforations and notches in the scales ; there is one 

 principal "lateral line" as usual, and a second proceeds above on each 

 side from the outer supraternporal plate to the origin of the dorsal fin. 

 The earliest satisfactorily -known species of Lepidotus is L. gallineki from 

 the Rhsetic of Upper Silesia ; and the typical species, L. elvensis, occurs 

 in the Upper Lias of Bavaria, Wiirtemberg, N. France, arid Northampton- 

 shire. Two well-known species are obtained from the English Oxford Clay, 

 and fine examples of other species are met with in the Lower Kimmeridgian 

 (Lithographic Stone) of Bavaria. L. minor (fig. 69) is well preserved in 

 the Purbeck Beds of Swanage, Dorsetshire, while L. mantelli is a well- 

 known large species from the English Wealden. Beyond Europe, charac- 

 teristic remains of Lepidotus have been fcmnd in the Jurassic of India and 

 the Cretaceous of Brazil. 



Dapedius (fig. 70). A genus most conspicuously differing from 

 Lepidotus in the comparatively deepened form of the trunk, the presence 

 of a gular plate, the elongation of the dorsal and anal fins, the uniserial 

 arrangement of the small fin-fulcra, and the form of the overlapped 

 portion of the scales, which is not produced at the angles. The chondro- 

 cranium is well ossified, and the basicranial axis is sharply bent upwards 

 in front of the otic region. The basioccipital appears as in Lepidotus 

 with some evidence of an extended basicranial canal ; and there is reason 

 to believe that the olfactory nerve extended across the orbital cavity as in 

 Lepidosteus. The membrane-bones of the cranial roof form a continuous 

 shield, and in adult individuals the paired parietals, froutals, and 

 squamosals are usually fused into a continuous plate. Immediately in 

 advance a pair of short and broad nasals meet in the middle line ; and 

 there is a small median plate enveloping the ethmoid in front. The 

 premaxillie are separate, small and short, apparently without any ascend- 

 ing process ; the maxilla is bounded above in its hinder two-thirds by a 

 small, narrow supramaxilla. The parasphenoid appears to have been 



