278 B. Smith — Note on the Miocene Drum Fish. 



the fossils are fragmentary, there can be no question as to their 

 osteological value when we compare them with the correspond- 

 ing parts which have been taken from the branchial arches of 

 the recent P. cromis (L.). 



Considering first the type of Pogonias midtideniatus, we 

 see that the bean-like crushing elements have all disappeared 

 leaving only their sockets, while the plate itself has lost much 

 of its outer and posterior portions. Some of the anterior part 

 is likewise gone. On its dorsal surface the most striking points 

 observed are (1) the ridge on the anterior central portion of 

 the plate leading backward to the knob, which in the recent 

 Drum serves for the attachment of the second epibranchial ; 

 (2) a portion of the large rounded knob at its posterior extrem- 

 ity, which in the living form furnishes the surface for the 

 attachment of the broadly expanded proximal end of the 

 fourth epibranchial ; and (3) the strong ridge and process on the 

 median margin, which is for muscular attachment. These 

 three features are unmistakable and can all be checked with 

 similar ones in the corresponding plate of P. cromis. Espe- 

 cially is this true for the large posterior knob, whose surface 

 bears the same minute wavy ridges which are found in the 

 living form. 



When, now, we examine the dorsal surface of the Maryland 

 fossil, we find, in spite of its fragmentary condition, that it 

 agrees in every structural feature with the second left superior 

 pharyngeal plate of P. cromis, and that there can be no ques- 

 tion of the position which it occupied in the pharynx. The 

 broken surface along the inner margin shows that the dorsally 

 directed ridge was here well developed. The ridge which led 

 to the knob for the second epibranchial attachment is unusually 

 sharp and strong, much more so than in the type, and in this 

 respect it closely approaches the condition observed in im- 

 mature examples of the recent P. cromis. 



Range and Probable Evolution of Pogonias. 



In Dr. Hay's "Bibliography and Catalogue of the Fossil 

 Yertebrata of North America "* two species of Pogonias are 

 listed. The first of these, P. cromis, is mentioned by Leidyf 

 as being found in the sands of the Ashley River, South 

 Carolina ; the second, P. multidentatus, was described by Cope 

 as having come from the Miocene Cliffs of Nomini, Westmore- 

 land County, Virginia. Inasmuch as the Calvert, Choptank, 

 and St. Mary's strata are all extensively exposed at this local- 

 ity,;); it is unfortunately impossible to tell from Cope's descrip- 



*Bnll. U. S. G. S. No. 719, Washington, 1901. 



f Indications of Twelve Species of Fossil Fishes, Proc. Acad. Nat. Sci., 

 Phila., vii, pp. 395-97. 



X Md. Geol. Surv. Miocene, pp. lxxix and lxxx. 



