NATURAL SCIENCES OF PHILADELPHIA. 36 



BRACHIOPODA. 



Chonetbs?? millepunctata, M. aud W. 



Shell attaining: a large size, very thin, transversely subsemicireular. or 

 more than twice as wide as long, with lateral extremities rounded. I>< 

 valve nearly flat, or but slightly aud evenly concave ; hinge line a little less 

 than the greatest transverse diameter; cardinal process rather stout, 

 with an obscure linear ridge (or sulcus) extending forward from its I 

 nearly to the front; cardinal edge slightly thickened within, so as to 

 form a faintly defined ridge extending about half-way from the cardi- 

 nal process toward each lateral margin, but apparently without any trace of 

 sockets for the reception of teeth in the other valve ; muscular aud other in- 

 ternal markings unknown; surface ornamented by numerous slender, exceed- 

 ingly regular, closely arranged concentric lines, exactly parallel with each 

 other and the front and lateral margins. (Ventral valve unknown.) 



Length of a medium sized specimen, 1-30 inch; breadth, 2-95 inches. 

 Largest examples seen, 2-10 inches in length, and of nearly the same propor- 

 tional breadth as the others. 



Of this very remarkable shell we have seen six or eight specimens, and 

 some fragments of others. All of the specimens yet found, however, are dor- 

 sal valves only, the ventral valve being entirely unknown to us. The slightly 

 worn, or more or less weathered condition of the specimens has obliterated 

 whatever muscular or other internal markings there may have been. In most 

 cases only patches of the shell itself remain, though, even in these cases, the 

 general outline and external surface markings are very distinctly defined in 

 the matrix. All of the specimens show a rather obscure, linear, internal sul- 

 cus extending from the base of the cardiual process nearly to the anterior 

 margin. This, however, is probably caused by the accidental removal of a 

 linear mesial ridge, because we also see it equally defined in impressions of 

 the external surface of the valve left in the matrix, just as would be the case 

 if a firm internal ridge had been, owing to the thinness of the shell, as it were, 

 pressed through. The concentric lines of the surface present an extraordinary 

 degree of regularity, both in size and arrangement. On a medium sized dor- 

 sal valve about sixty of these lines may be counted, while some of the largest 

 show twice as many. They are of exactly the same size and distance apart 

 on all the specimens, and of so nearly the same size on all parts of the same 

 individual as to appear to the eye to be exactly uniform throughout. By 

 measurement, however, we count fifteen of them in the space of 0-25 inch 

 near the margins of a medium sized specimen, and twenty in the same space 

 near the beak. In a few instances we have observed what seemed to be the 

 faintest possible traces of a few larger radiating lines or cost*, near the mid- 

 dle of the anterior margin of the dorsal valve. None of the specimens show 

 the cardinal process entire, but as far as its characters can be made out it 

 seems to have been much as in Chonetes. 



The most remarkable character of this shell, however, remains to be men- 

 tioned. That is, its extremely coarse punctate structure, and the unusually 

 close arrangement of the punctures, which are so large as to be nearly visible 

 to the unassisted eye. As seen by the aid of a common single pocket lens, 

 they present, on the inner surface of the dorsal valve, much the appearance 

 and arrangement of the cells of a delicate Ckxtetes, the spaces between them 

 being much less than the diameter of the pores themselves. They appear to 

 diminish rapidly in size, however, as they approach the external surface, near 

 which they seem to be a little less than the diameter of the spaces by which 

 they are separated. As we have never seen such a shell structure as this in 

 any species known to possess the characters of the genus Chonete*, nor indeed 

 in any other known Brachiopod, we are very strongly inclined to believe our 

 shell really belongs to an undescribed genus. The fact that there appear to 

 be no sockets in the cardinal margins of its dorsal Talve, for the reception oi 



1870.] 



