Cope.] 45b [Sept. 15, 



along the external margin. Pterygoid bone ending in a free decurved 

 edge anterior to the quadrate bone. Palatines and pterygoids narrow, 

 leaving a wide palatal foramen. Vertebrae in their principal features as in 

 Eryops. The humerus is unlike any of those enumerated in my synopsis of 

 Permian humeri,* but resembles the one figured by Gaudry as belonging to 

 Aetinodon, except that in Acheloma there are no condyles, and there is an 

 epicondylar foramen. This is the first time I have observed the foramen in a 

 Batrachian, though it is universal, so far as known, in the Pelycosauria. 

 As in Aetinodon, there is a short process above the external epicondylar 

 angle. 



The absence of humeral condyles in this genus is paralleled by the same 

 feature in Glepsy drops natalis. It looks as though the animal were young, 

 and had not yet attained to the coossification of epiphyses. This theory may 

 account for the condition of the humeri in the two species mentioned. It 

 occurs equally in the T rimer orhachis insignis. As all these species show 

 every other indication of maturity, and as I have never yet observed free 

 epiphyses in any of my numerous Texan collections, I am disposed to 

 look on this condition of the humeri as a case of permanent incomplete- 

 ness, of which the Batrachia present so many instances. 



ACHELOJIA CUMMINST, Sp. UOV. 



This animal is represented by a greater part of a skull and vertebral 

 column, with both humeri and scapulae and various other bones of the 

 limbs, including phalanges. All of these remains look a good deal like 

 Eryops megacephalus, and they might be supposed on hasty examination 

 to belong to the young of that species. On a full investigation the follow- 

 ing differences appear, besides those already mentioned in the generic 

 diagnosis. 



The muzzle is relatively much shorter, and the extremity is less de- 

 pressed ; the length from the supraoccipital forwards, is a little less 

 than the total width at the same point. In agreement with this, the man- 

 dibular rami, after diverging strongly from the symphysis, are strongly 

 incurved to the quadrate, a form not found in E. megacephalus. The 

 sculpture is more sharply defined in the present species. In the vertebrae, 

 although the intercentra have the same degree of ossification as in the E. 

 megacephalus, the neural spines have not the expanded head of those of 

 the larger species, but look as though they had lost an epiphysis, as in the 

 case of the humeri. They are erect, with subquadrate section, and not 

 oblique and grooved as Trimer orhachis insignis. The diapophyses are more 

 elongate than in E. megacephalus, and their extremities frequently -have a 

 subround or suboval section, and but few have the narrow surface seen in 

 E. megacephalus. The ribs are short and flat, and have the distal extremities 

 expanded paddle-shape. Laid backwards such a rib reaches to the poste- 

 rior edge of the third diapophysis posterior to the one to which it is 

 attached. 



♦Proceedings American Philos. Soc, 1878, p. 528. 



