220 BULLETIN OF THE 



epiphysis. In this section it will be seen that a distinct line of demar- 

 cation exists between the true epithelial portions of the two walls 

 where they come in contact. This distinctness is maintained through- 

 out the entire series of sections. When the median section is reached, 

 the vesicle has entirely disappeared. From the distal end of the vesicle 

 the connective-tissue string extends forward to the region of the eye, as 

 in the case of the proximal portion (con't. tis.). The blood sinus (Fig. 

 12) does not, in this species, come in contact with the epiphj'sial vesicle, 

 but occupies the same position on the proximal part as in the case of 

 P. Douglassii. It is much smaller in P. coronata, but in other respects 

 is of the same nature. Whether or not this epiphysial vesicle may 

 be homologized with the secondary vesicle in Petromyzon "(Ahlborn, 

 '83, Beard, '89, Owsjannikow, '88, Wiedersheim, '80) can be proBtably 

 discussed only after its development has been studied. So far as the 

 condition in the adult is concerned, there is little to indicate such a 

 homology. 



I mention here an observation which may be of significance in con- 

 nection with this complicated structure of the epiphysis. In both spe- 

 cies and in all the individuals of Phrynosoma of which I have made 

 sections favorable for exhibiting the entire dorsal surface of the brain, 

 I have noticed that the pia mater appears to form a jimction with the 

 coimective-tissue string described as passing from the distal extrem- 

 ity of the epiphysis to the region of the parietal eye, and also that it 

 is thrown into several folds on the dorsal surface of the cerebellum. 

 The membrane where folded is considerably thicker than elsewhere, 

 contains within its folds numerous blood-vessels, and is com.posed of a 

 single layer of cells very regular and distinct in outline and of a de- 

 cidedly epitheloid appearance. The condition reminds one strongly 

 of the folded portion of the wall of the epiphysis. 



Uta Stansburiana. 



As I have had but two specimens of this species, both preserved in 

 alcohol, and hence not in the best histological condition, my study of 

 it has been less satisfactory than that of the species of Phrynosoma. 

 A few points, however, have been observed which are of some interest; 

 but these can be presented without entering into a detailed descrip- 

 tion of the structure. Figure G (Plate II.) represents a portion of a 

 sagittal section through the dorsal wall of the head and the parietal 

 vesicle. The parietal foramen, too broad to be embraced in the figure. 



