MK. J. W. DAVIS ON HETEEOLEPIDOTTJS &EANDIS. 293 



On Heterolepidottis grandis, a Fossil Fish from the Lias. 

 By James W. Davis, F.L.S., F.G-.S. 



[Eead 6th November, 1884.] 



(Plate VII.) 



Genus Heteeolepidqttjs, Egerton. 



Head large ; snout obtusely conical ; maxillary and mandibular 



bones straight ; teethi of various sizes, the larger ones strong and 



bluntly pointed, the smaller ones sharp and numerous ; gape 



wide ; pectoral and ventral fins large ; dorsal fins remote ; scales 



large, thick, and lustrous, more or less serrated on the posterior 



margins ; abdominal scales small and elongated ; tail broad, the 



upper lobe ridged, with strong fulcral scales. {Egerton.) 



Heteeolepidotus geakdis, sp. nov. 



The fossil fish wMch serves as subject for the following descrip- 

 tion is a remarkable specimen, measuring 40 inches in length. 

 Its bony structure is preserved and well exposed, whilst the 

 scales, which are apparently thin, are preserved only in patches, 

 principally on the anterior dorsal and ventral surfaces of the 

 fish. The head is not well preserved ; its component bones are 

 disturbed and dissociated. A mass of iron pyrites envelopes the 

 bones of the vertebral column from its connexion with the head 

 backwards as far as the anal fins, beyond which the vertebrae are 

 well defined. 



The particulars following give the size and relative proportions 

 of the fish : — 



Length , 40 inches. 



Depth behind the pectoral fin 8 „ 



Depth between the dorsal and ventral fins . 6 „ 



Depth at the base of the tail 3*5 „ 



Diameter between the extremities of the 



lobes of the tail 10*5 „ 



Length of the head 8 „ 



Occiput to dorsal fin 11 „ 



Base of dorsal fin 5 „ 



Dorsal fin to base of caudal 10 „ 



Anterior of pectoral fin to ventral 12 „ 



Anterior of ventral fin to anal 6 „ 



Anterior of anal to base of caudal fin ... . 7 „ 



A comparison of these measurements with those given by Sir 

 Philip Egerton (Memoirs of the Geological Survey, decade xiii. 

 plate 3), in the description of Seterolepidotus latus, shows that 



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