N. ROSÉN, STUDIES ON THE PLECTOGNATHS. 13 



the skull of Balistes and M onacanihus . Balistes has been the 

 object of SupiNO's studies. He bas given a description from 

 a modern point of view. As to tbe homolog}^ of tbe bones 

 I quite agree with Supino. Referring to bis figures, I sball 

 give below a sbort account of tbe skull. Some cbaracters 

 of interest wbicb have not been mentioned b}^' previous wri- 

 ters will be pointed out. 



Supraoccipitale corresponds to Hollard's interparietal. 

 HoLLARD describes erroneously a portion of tbe epiotics as 

 supraoccipitale, according to which opinion the supraoccipi- 

 tal would be paired. Supraoccipitale lies mainly between the 

 two frontals. It is displaced cranially in Monacanthus more 

 than in Balistes. A large supraoccipital crest is developed. 



Occipitale laterale. The two lateral occipitals touch each 



other in the dorsal median line, thus bordering the occipital 



foramen dorsally 



Basioccipitale does not show any pecub'arities. 



Epioticum. The two epiotics are extraordinarily large 

 and touch each other in the dorsal median line between the 

 supraoccipitale and the lateral occipitals. Behind the sup- 

 raoccipitale there is a foramen which is bordered caudally 

 by the epiotics. The foramen is occupied by a process of 

 the supporting-apparatus of the anterior dorsal fin. It is a 

 part of the occipital foramen which has been separated by 

 the median development of the lateral occipitals and the 

 epiotics on one side and the cranial displacement of the sup- 

 raoccipital on the other side. 



Prooticum is very small. Sphe7ioticum is present. 



Parietale. No distinct parietals can be recognized. They 

 have perhaps fused with the frontals. 



Frontale is paired. According to Hollard, the both 

 bones are united anteriorly; but neitber Supino nor the pre- 

 sent writer have found this to be the case in Balistes. 



Supraethmoideum. The large bone which Hollard de- 

 scribed as several elements, viz. the unpaired nasal and the 

 paired ethmoids, I consider, with Supino, to be the supraeth- 

 moideum. The nasals lie in all teleosts laterally to this 

 bone, but are absent in the Balistids as well as in all other 

 Plectognaths. Supraethmoideum is provided with an arti- 

 cular surface for the praemaxillaries and the maxillaries. 



Ethmoideum laterale has an artlcular surface for palatinum. 



