DEVONIC FISHES OF THE NEW YORK FORMATIONS 



51 



specimen nor in any previously figured appendage are their boundaries 

 clearly discernible. 



Only a few fragmentary examples of the head shield have thus far 

 been obtained. One such belonging to the Museum of Comparative 

 Zoology at Cambridge, Mass. is notable for having the orbital region well 

 preserved, with the pineal element in place, and for exhibiting both 

 external and internal (visceral) aspects of the postmedian plate. Two 

 shallow rounded pits, similar to those that have already been observed in 

 B. canadensis and Asterolepis maxima, but separated by a 

 small, tumid T-shaped septum, occur in about the center of the latter plate 

 on the inferior surface. The pineal plate is much larger than the corre- 

 sponding element in other species, and is semicircular in outline, instead of 

 quadratic. A tubercular swelling seen on the dorsal surface would seem 

 to indicate the presence of a pineal pit beneath. No other plates remain 

 in the orbital opening of the specimen in question. 



The fact has already been noted by Newberry and Smith Woodward 

 that in the groups of detached plates belonging to this species, the large 

 anterior dorsal is more numerous than any of the others, its greater 

 frequency being ascribed by these authors to sorting of material through 

 current action during deposition of the sediments. One might suppose, 

 also, that this plate was better able to withstand injury on account of the 

 solidity imparted to it by the strong median keel running along the median 

 line of the under side. At all events it is certain that the keelless postero- 

 dorsomedian plate is far Less commonly preserved. 



Formation and locality. This species occurs typically and in great 

 abundance in the Catskill of Tioga county, Pennsylvania, but has been 

 reported from but a single locality in New York State, along the line of the 

 Ontario and Western Railroad between Merrickville and North Walton, in 

 Delaware county. 



