A FOSSIL FISH FROM THE LIAS. 297 



of EugnatJius on the same region of its body. The teeth of 

 Lepidotus are of two kinds — obtusely pointed and uniform in size 

 in the jaws, or rounded and palatal like those of the Pycnodonts ; 

 in the genus now considered the teeth are numerous, pointed, and 

 may vary in size. The specimen described above agrees with 

 Egerton's definition of the genus Heterolepidotus in possessing 

 elongated scales on the ventral region of the body and in having 

 sharply pointed teeth, but in this specimen the teeth appear to 

 have been uniform in size, and in this respect it differs from either 

 of the two species described in the 13th decade of the Memoirs 

 of the Greological Survey. The scales also, whilst conforming to 

 the generic requirements, are thin and pustulate and devoid of 

 serrations on their posterior margin, whereas in those already 

 described the scales are thickly coated with ganoine and have the 

 margins serrated. In form this example is more nearly related 

 to the slim H. sauroides from Barrow-on-Soar than to the thick- 

 bodied H. latus of Lyme Eegis. The bony skeleton of the spe- 

 cimen now described is more satisfactorily exhibited than has 

 perhaps previously happened, and it exposes some points of con- 

 siderable interest ; amongst others, the attachment of the dorsal 

 and anal fins, with the series of well-developed interspinous 

 bones, the peculiar arrangement of the articular apparatus of 

 the pectoral fins, and the heterocercal form of the tail. Sir 

 P. Egerton considered that the caudaJ fin of the Heierolepidoti 

 was of strictly homocercal form ; but it is evident from this spe- 

 cimen that the fin-rays are wholly supported from the haemal 

 surface of the spine, and that only the fulcral plates are supported 

 from the neural — an arrangement which is the same as that in the 

 living Lepidosteus, though the form of the tail in the latter is 

 externally diphycercal, whilst that now described is deeply forked. 



"Whilst it is evident that in m.any particulars the specimen now 

 described does not clearly coincide with the characters of the 

 genus Heterolepidotus as defined by Egerton, it is nevertheless 

 undesirable to multiply genera, and it is proposed to include this 

 species in the genus Heterolepidotus, with the specific appellation 

 of grandis. 



The figure of the specimen has been reduced to one third the 

 size of the original by Mr. Henry Sykes, to whom I am much 

 indebted for the careful and admirable manner in which the 

 drawing has been rendered. 



Formation and Locality. Lias : Lyme Eegis. 



