Cope.] ^" [May 7, 



surface of the cranium is thrown into wrinkles which form no regular pat- 

 tern, and which inosculate to a moderate extent, most so on the preorbital 

 region. The anterior parts of the maxilliary and mandibular bones are 

 marked with small pit- like impressions. 



Measurements. M. 



Total length to quadrate ansles measured on median 



line '^. 170 



Length to supraoccipital border 138 



Total width posteriorly 155 



Width at orbits 095 



" between orbits '. . .031 



" at nares 062 



" between nares 030 



Long diameter of orbits 026 



Transverse diameter of occipital cotylus 012 



This cranium is much shorter and wider than that of Archegosaurus 

 decheni, and has the orbits more anteriorly placed. 



CROSSOPTERYGIA. 



ECTOSTEORHACHIS Cope, gen. nov. 



Tribe Crossopterygia ; family Bhombodipteridce Traquair ; sub-family 

 Saurodipterini Huxley. Pectoral and ventral fins rather acutely lobate, 

 with few or no radii on their external borders. Dorsal and anal fins un- 

 known. Scales imbricate, rhombic, smooth. Ganoine wanting from top 

 of head in specimens examined, but present on sides and inferior surfaces. 

 Coronal suture distinct. End of the muzzle covered with separate scales. 

 Distinct sub- and postorbital bones. Gular bones, an anterior azygus and 

 two laterals on each side, the posterior the shorter. Teeth acutely conic, 

 rather small ; a few large ones at the anterior part of each jaw. Verte- 

 bral centra represented by osseous rings which enclosed a notochord. 



This new genus is apparently nearly related to MegalicMhys, and in a 

 less degree to Osteolepis and Diplopterax. Pander, Miller and others repre- 

 sent the ventral fins of the two genera last named as not lobate, but sessile, a 

 state of things entirely diflerent from what is observed in EctosteorhacMs. 

 The sub-division of the dermal bones of the muzzle is also rather character- 

 istic of Megalichthys. From the latter genus it difiers in the form of the 

 vertebral centra. Both Agassiz and Huxley describe those of Megalichthys 

 as completely ossified, and as biconcave. In Ectosteorhachis they are repre- 

 sented by annular ossifications resembling somewhat those of the stego- 

 cephalous genus Cricotus, but with a larger fo7'ainen chordcB dor salts. 



The elongate-lobate axis of the fins of this genus render it probable that 

 those of Megalichthys present the same character. 



Ectosteorhachis nitidus Cope, sp. nov. 

 This fish is represented by several specimens, the best preserved of which 

 includes the head and body inclusive of the ventral fins. These form an 

 ichthyolite nearly denuded of matrix, the inferior side being best preserved. 



