ANIMALS. 233 
PYGOPTERUS MANDIBULARIS, Agassiz. De Verneuil, Bull. Soc. Géol. de France, 2™ série, 
vol. i, p. 41, 1844. 
say sans A Geol. Russ., vol. i, p. 227, 1845. 
» Tennant, Strat. List, p. 89, 1847. 
King, Catalogue, p. 15, 1848. 
Howse, Trans. T. N. F. C., vol. i, p. 236, 1848. 
— — ” 
The specimen of Pygopterus mandibularis represented in Pl. 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 Humboldiu. 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 mandibularis occurs in Mar!-slate at Whitley, Cullercoats, Kast Thickley, 
Ferry-Hill, and Thrislington Gap. The specimen figured, and belonging to the Museum 
of the Yorkshire Philosophical Society, is from the last locality. - 
Pycorrerus LAtuS, Hyerton. Plate XXIV, fig. la. 
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 imches and a half deep at the shoulder, and a trifle less at the 
ee 
