ANIMALS. 233 



Pygopterus mandibularis, Agassiz. De Verneuil, Bull. Soc. Geol. de France, 2"" serie, 



vol. i, p. 41, 1844. 



— — „ Geol. Russ., vol. i, p. 227, 1845. 



— — „ TenDant, Strat. List, p. 89, 1847. 



— — ,, King, Catalogue, p. 15, 1848. 



— — „ HovFse, Trans. T. N. F. C, vol. i, p. 236, 1848. 



The specimen of Pygoptenis mandihularis represented in PI. XXIII, fortunately 

 supplies all parts of the fish deficient in those examined by Professor Agassiz, viz. 

 the pectoral and ventral fins, the anterior portion of the body, and the scapular arch. 

 The ventral fins are situated about midway between the pectoral and anal fins : they 

 are remarkably small as compared with those organs in the genus Acrolepis. The 

 pectoral fins are of large size, and composed of a considerable number of rays, divided 

 and subdivided into fine fimbriations at their distal extremities : they are more 

 pointed and not so large as the pectoral fins of Pygopterus Humboldtii. The bones 

 composing the scapular arch are thick and strong, in harmony with the entire 

 organization of this fish, adapted as it is for swift progression and predatory power 

 of no ordinary degree. The scales on the anterior part of the fish are neatly and 

 distinctly sculptured somewhat after the pattern of the scales of Acrolepis ; but this 

 ornamentation does not extend beyond the insertions of the ventral fins. It is most 

 probable^ that the, Pygopterus sculptus, alluded to by Agassiz at page 77, may have been 

 suggested by a specimen of the anterior portion of the species under description. — 

 P. G. E. 



Pygopterus mandihularis occurs in Marl-slate at Whitley, Cullercoats, East Thickley, 

 Ferry-Hill, and Thrislington Gap. The specimen figured, and belonging to the Museum 

 of the Yorkshire Philosophical Society, is from the last locality. 



Pygopterus latus, Egerton. Plate XXIV, fig. 1 a. 



This very distinct species of Pygopterus differs from the other members of the 

 genus in the greater depth of the body, as compared with its length. The only 

 specimen I have seen is in my own cabinet. The bones of the head are dislocated, 

 and the lower extremity is wanting from the point where the vertebral column bends 

 upwards to form the heterocercal tail ; but the trunk is perfect, with the exception 

 of the external rays of the fins. It measures twelve inches and a half in length 

 from the insertion of the pectoral fin to the commencement of the lower lobe of 

 the tail, and is five inches in depth at the shoulders, decreasing to four inches 

 and a half at the dorsal fin. A very perfect specimen of Pygopterus mandibularis 

 (the one above noticed, with which I have compared it), twelve inches in length, 

 is only three inches and a half deep at the shoulder, and a trifle less at the 



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