90 PALAEONTOLOGY OF KENTUCKY. 



Surface is marked by strong, rounded plications. The sinus is bounded by 

 a strong rib on each side ; this rib bifurcates below the umbo, and the branch 

 next to the sinus drops into it, and at the front coalesces with the elevated 

 flange of its extension ; another rib starts in the bottom of the sinus in front of 

 the umbo, and extends to the termination of the sinus, having sometimes 

 bifurcated at about the middle of its length. The mesial fold has generally 

 two plications on its summit and one on each of its lateral slopes, but the top 

 ribs are often increased by bifurcation before they reach the front. On each 

 side of the mesial fold and sinus there are about five or* six plications, of 

 which only two reach the apex; the others were added, partly by bifurcation, 

 partly by interpolation. Other surf ace- markings are not visible. 



Formation and Locality. Found in the Niagara group in the quarries east of the city of Louis- 

 ville, Ky. Although rare, some very fine specimens may be seen in some of the Louisville collections. 

 This species has in its general outline some resemblance to Khynchonella whitii, of the Niagara rocks from 

 Waldron, Indiana, but it differs from it by its peculiar plications, and by the marginal flange of its ventral 

 valve, which two features are sufficient to distinguish it at the first glance from that species. A still 

 greater resemblance has it to Atrypa nodostriata, as figured by Prof. Hall in Pal. of Ohio, Vol. 2, plate 7, 

 figures 12, 13 and 14, and described in same volume, page 133. Differences between these figures and our 

 shells exist only in one or two minor points, which are easily accounted for by the fact that the Ohioan illus- 

 trations were made from an exfoliated cast, while my specimens are perfect shells. In consequence of this 

 great resemblance, which amounts almost to indentity, I placed my shells, at first, in the species of A. 

 nodostriata. But when I examined Prof. Hall's original description and figures of that species, in Pal. N. 

 Y., Vol. 2, page 272, and plate 56, figures 2a-n, I could not identify my specimens by either. It appears to 

 me that the description and illustrations in the New York Keport are entirely different from those of the 

 Ohio Keport. By the New York description and figures the species is established. The Ohio shell, which 

 is only an exfoliated cast, belongs, undoubtedly, to one and the same species with my specimens, but not to 

 Atrypa nodostriata of the New York Report. For these reasons I have to establish a new species for the 

 reception of my specimens and the cast figured in the Ohio Report, and I name this species in honor of 

 Prof. Samuel Calvin, of Iowa City, Iowa, who ranks as scientist with the foremost of this country, and 

 whose labors in Geology and Palaeontology have greatly contributed to the wonderful progress made by 

 those sciences in the latter half of the present century. 



Atrypa ellipsoida. N. SP. 



Of this beautiful shell I have two specimens in my collection, and if I am 

 not mistaken, I have seen one or two in some other cabinets. It took me some 

 time before I could come to a conclusion, whether to leave it with Atrypa 

 reticularis, which it resembles in every feature, except the form, or to place 

 it into a new species. I have decided to take the latter course, and I hope 

 future developments in regard to this shell will prove my decision to be cor- 

 rect. The description of this new species is as follows : 



Shell, 'in proportion to the common size of our A. reticularis, rather small ; 

 longitudinally sub-elliptical, the shell forming almost a regular ellipsoid ; 

 length about one and one-half its width, while its depth, measured at the 



