xo. 1696. AIR-BREATHING VERTEBRATES— MOODIE. 25 



in Ptyonhis we may conclude that the body was flattened from side 

 to side and that the caudal region was provided with a membraneous 

 fin, such as is found in the recent Petrow/yzon and its allies. 



Ptyomus is a t3'pical member of the Aistopoda, the chief character 

 of which group is the absence of limbs. With this character are, how- 

 ever, associated a concomitant lengthening and attenuation of the 

 facial region, a recession of the orbits, an elongation and an attenua- 

 tion of the body, a tendency to flattening from side to side in the 

 vertebrae, an increase in the length of the tail, and the production 

 of a peculiar type of abdominal armature, consisting of small rods 

 arranged in a chevron pattern, ranging from just back of the skull 

 in the pectoral region probabl}^ to the anus. 



In other species of the genus PtyonhiH the pectoral plates are moro 

 highly developed than in P. pectinatus Cope and especially in P. 

 nummifer Cope. This is to my mind almost conclusive evidence that 

 the Aistopoda are a degenerate branch of the Microsauria, to which 

 they are closely related in most respects. The order Aistopoda may 

 be retained for the present, however, until future discoveries teach 

 us differently. 



DICERATOSAURUS PUNCTOLINEATUS Cope. 



It is with much gratification that a second specimen (Cat. No. 4461, 

 U.S.N.M.) of this peculiar species is to be recorded from the collec-. 

 tions in the U. S. National Museum. It supplements in a beautiful 

 manner the type specimen, as well as those described by Jgekel from 

 the collections in Europe. In the present specimen the head is lack- 

 ing. There are nineteen vertebrae preserved, and nine pairs of ribs. 

 The ilium is present as a mold in the soft coal, and the femur and 

 tibia (?) of the hind limb are preserved. The principal ncAV char- 

 acters which are added to the knowledge of the species by this speci- 

 men are the presence of the peculiar ilium and the large leg. 



The vertebra? have the same character as the type. The ribs are 

 intercentral and do not differ from the type as to structure or form. 

 They are but slightly curved and are of an almost luiiform width, 

 with the head large. The mold of the ilium is liourglass shaped. It 

 Avas evidently in the shape of a flattened plate with a rounded short 

 shaft. It apparently attaches to the seventeenth vertebra? in the series 

 as preserved. Since there are very probably two or three vertebrae 

 gone from the cervical region, the sacral was probably the nineteenth 

 or twentieth vertebra of the series. The body of the animal was 

 stout, as is evidenced by the dimensions of the skeleton. 



There are no traces of ventral sciitella^. These structures are scant- 

 ily preserved in the type specimen, and Jaekeldid not find them at all 

 in the forms studied by him. The dimensions of the entire leg are 

 those of PeJion lyelU Wyman, and at first sight it was thought that 



