NATURAL SCIENCES OF PHILADELPHIA. 273 



PHYSOPYXIS, Cope. 

 Proceed. Acad. Nat. Sci. Phila., 1871, 113. Genus novum doradi affine. 



Dorsal fin with strong pungent spine, in advance of the ventrals. 

 Gill openings much reduced, opercular apparatus attached to 

 clavicular arch below. No adipose dorsal; anal fin short; vent 

 median ; nares close together, the posterior minute. Barbels well 

 developed, one maxillary and two mental on each side. Mouth 

 terminal, teeth minute in several series. 



Sides and dorsal part of the body entirely inclosed by vertical 

 osseous shields. Head and thoracic region inclosed in a trihedral 

 osseous box, composed of the expanded cephalic casque above, 

 clavicular arch laterally, and the immense development of the 

 clavicles and coracoids inferiorly. These form a shield, which 

 extends to beneath the eyes anteriorly, and sends two postcora- 

 coidea posteriorly, all entirely involving the derm. Pectoral 

 spines and swim-bladder greatly developed. 



This strange genus carries to its highest extreme the peculiar 

 features of Doi^as. Thus the branchial fissures are still more re- 

 duced, the operculum being attached all along its inferior margin; 

 the lateral osseous dermal scuta are prolonged upwards to the 

 median dorsal line; the pectoral spines are immensely developed. 

 It differs further from Doras in the greater development of the 

 inferior elements of the scapular arch and the entire occupation 

 of the skin by the ossification. The swim-bladder is large, and 

 extends to the skin on each side of the casque and above the 

 humeral processes, and between the long postcoracoid processes 

 on the inferior surface. The osseous box inclosing the anterior 

 half of the body protects this swim-bladder, but the teleologist 

 will suggest that perhaps, on the other hand, the large swim- 

 bladder is necessary to float the heavy shields and defensive 

 spines. 



The small body and immense casque give this form a very pe- 

 culiar appearance, and suggest a miniature iron-clad with mast 

 and outriggers. 



PHYSOPYXIS LYEA, Cope, sp. nov. 



Muzzle short and broadly truncate, about as long as the dia- 

 meter of the eye, lips even. Interorbital region concave, thrice 

 as wide as the diameter of the orbit, with an oval median fonta- 



1872.] 



