802 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. [56] 



better ossified than the others. There are altogether four of them, and 

 they are much compressed from side to side. The arches proper are 

 five in number, the first four being complete, with the usual elements 

 present. They are completely beset with groups of minute teeth, which 

 ride them above, and come off like scales during maceration. The gill- 

 rakers are very small and thick-set. 



Mr. Bridge completes his article in the Journal of Anatomy by a very 

 valuable and concise summary. As this occupies but little more than a 

 page, and contains so much, and in such a convenient form, of use in the 

 present connection, I feel quite sure the reader will think me warranted 

 in reproducing it here, and no doubt be thankful for it. 



This author says that "In summarizing the result of the foregoing 

 description of the skull of Amia, I would lay stress on the following 

 facts, as having a special bearing on the affinities of Amia to the more 

 highly specialized osseous fishes and to the amphibia. 



"I. The possession of a complete chondrocranium, *. e. the absence of 

 fenestrse in the cranial roof, as in Lepidasteus and the Pike (Esox). 



"II. The existence of a nearly complete series of otic bones, compris- 

 ing a large pro-otic, with internal plates forming a characteristic "pro- 

 otic bridge" in the floor of the cranium, opisthotic, epiotic, and sphe- 

 notic elements. 



"III. The presence of two ossific centers, partly exosteal and in part 

 endosteal, forming rudimentary basisphenoid. 



"IV. Septo-maxillary ossifications in the subnasal lamina, as in 

 Clarias, Esox, Eana, and Ophidia. 



"V. The interorbital prolongation of the cranial cavity, separating 

 distinct, paired ali- and orbitosphenoids. 



"VI. The prolongation of the palatine in front of its prefrontal artic- 

 ulation, and the connection of its anterior end with the inwardly 

 curved process of the maxilla. 



"VII. The possession of a T-shaped dermal ethmoid overlying the 

 premawillce, and the close analogy in number and relations between the 

 investing ganoid plates of Amia and those of the Siluroidei, and espe- 

 cially with those of Clarias, as has been previously described. 



"VIII. A complete series of opercular bones, a preoperculum anchy- 

 losed to the hyomandibular and symplectic bones, an operculum, an 

 interoperculum, and a suboperculum. 



"IX. The presence of a jugal bone [admaxillary (a)] attached as in 

 Teleostei to the upper edge of the posterior part of the maxilla. 



"X. The existence of a mento-meckelian ossicle, as in Spatularia, and 

 of several additional centers of ossification in the proximal extremity 

 of Meckel's cartilage. 



"XI. The presence of five accessory dentigerous splenial elements in 

 addition to the normal mandibular splints, as in the young Polypterus 

 and Ceratodus among Ganoids, and in Siren and larval Salamanders- 

 amoug Amphibia. 



