CACOPS ASPIDEPHORIS ZO.) 



each condyle there are the usual two cranial foramina at the base of the 

 ])aroccipital processes, which extend outward, joining the epiotic 071 the 

 under side and turning downward to terminate at or near the upper 

 posterior corner of the quadrate. Between this paroccipital process and 

 the roof, at each side, there is a moderately large post-temporal vacuity 

 leading into a deep cavity just inside the "tympanic" rim of the ear 

 cavity and below the roof of the skull. 



The structure of the under side of the skull, while not departing far 

 from the usual stegocephalan type, is somewhat remarkable. The palatal 

 cavity as a whole had a high arched roof, with a slender, almost vestigial, 

 parasphenoid dividing the large pterygoidal vacuities so characteristic of 

 the amphibia. The internal nares are larger than the external ones, situ- 

 ated either side close to the teeth, with their front margin almost below 

 the hind margin of the external nares. On the inner side of each there 

 is a stout, conical, recurved tooth, about 10 or 12 millimeters in length, 

 and another like it is situated near the posterior margin of the orifice, 

 not far from the maxillary teeth. These are the only teeth located on 

 the palatal surface. The palatines, or conjoined palatines and pterygoids, 

 on each side posteriorly and internally to the nares slope strongly upward. 

 In the middle in front the vomers or anterior end of the parasphenoid 

 is about 15 millimeters in width where it joins the palatine shelf, nar- 

 rowing to about 4 where it joins the rhinencephalic chamber. Posteriorly 

 the an-angement of the basicranial bones is very similar to that of Trema- 

 tops or Eryops. The ossified basisphenoid sends downward and outward 

 a stout basiptervgoid process to join the pterygoids on each side, the 

 juncture indicated by a thickening as in Trematops. Outwardly the 

 pterygoids form a vertical plate, probably with the conjoined epiptery- 

 goids, reaching to the cranial wall, save for a small vacuity near the roof, 

 leading into the deep temporal cavity under the roof, into which the post- 

 temporal vacuity also opens, a cavity open below back of the pterygoids 

 between the basicranial bones and the posterior wings of the pterygoids. 

 In the middle the parasphenoid continues forward from the basisphenoid 

 as a slender rodlike bone nearly to the flat anterior end. For a short 

 distance it forms a high bridge, above which in front is the inferior 

 opening of the parietal foramen. For the larger part of its distance, 

 however, it is closely united as a thick ridge to the lower side of the 

 elongated rhinencephalic chamber (see plate 7 and plate 8, figure 1). 

 Between this chamber and the closed brain-chamber behind there is a 

 large orifice on each side for the escape of the optic nerves. This elon- 

 gated arched chamber has its anterior borders also free and curved a little 

 back of the anterior mardn of the orbits. In front of this the roof of 



