2 



BRITISH FOSSILS. 



being more slender than the former, and less so tlian the latter. 

 In general appearance it is not unlike the common Belone of our 

 British seas. The specimen selected for description has been kindly 

 lent for that purpose by the authorities of the Dorchester Museum. 

 It measures 13 inches from the snout to the base of the caudal fin, 

 and 1| inch in depth at its greatest diameter. The head measures 

 S-r%- inches in length ; nearly 1 inch of this measurement being due 

 to the prolongation of the rostrum beyond the symphisis of the 

 lower jaw. This portion of the snout is characterized by deep 

 longitudinal striae, while the base is perfectly smooth. The sur- 

 face of the cranial bones, but more especially of the prefrontals, 

 is studded with small granules interspersed with ridges of enamel 

 grouped together in an elegant pattern, and arranged for the most 

 part in a longitudinal direction. The lower jaw has a single row of 

 small close set tubercles on its median line. In advance of the 

 blunted extremity of the symphisis of the rami, a single, solid, conical 

 osselet is articulated, forming the apex of the lower jaw. This pecu- 

 liar structure is common to all the species of Aspidorhynchus, but 

 does not, so far as I am aware, occur in any other genus. The orbit 

 is large, and situated near the angle of the jaws. The latter are 

 furnished with a formidable array of sharp incurved teeth. Those of 

 the lower mandible appear in the specimen figured to have been the 

 largest ; but a portion of an upper jaw in my possession leads me to 

 conclude that the armature of the upper maxillary bone was not at 

 all inferior in power to that of the lower maxillary. All the teeth 

 appear to be quite smooth. The opercular apparatus is defective. 

 The operculum Is wanting, but owing to this, perhaps lucky, acci- 

 dent, the bronchial arches are exhibited ; parts rarely preserved in 

 the fossil state. The sub-operculum is small, and apparently smooth. 

 The pre-operculum, on the contrary, is large, and ornamented on 

 its lower limb with a row of distinct plaits of enamel. The pos- 

 terior angle is nearly a right angle. The pectoral fins are much 

 mutilated ; they appear to have been small, and to have been sup- 

 ported by a feeble thoracic arch. The ventral fins are also much 

 broken. They are situated 8 inches from the snout, and 5 from 

 the tail. The rays composing them are broad, and the transverse 

 articulations are numerous. The anal fin is inserted 2| inches from 

 the base of the caudal fin. The anterior rays are long, and bifurcated 

 at their extremities, but the succeding ones decrease rapidly in length, 

 giving a slender and pointed character to the fin. The number of 

 YSiys is uncertain, but they seem to have been not fewer than 14 

 or 15. The dorsal is the most remote of all the fins, its origin being 



