NATURAL SCIENCES OF PHILADELPHIA. 115 



The young of P. concentrica, Shumardiana, pyxidata, Cooperensis and arcu- 

 ata, present resemblances so strong that it is scarcely possible to distinguish 

 them from each other. In the adult state, however, the last may be distin- 

 guished by its much stronger and regular costae, its less rapid expansion and 

 greater arcuation. P. Cooperensis has the form of P. arcuata, without its 

 strongly marked ribs. The other three species are not satisfactorily distin- 

 guishable, even in the adult state. P. pyxidata was described by Hall from 

 the so-called Hamilton shale and limestone of Hamburgh, 111., and Louisiana, _ 

 Mo*; P. Shumardiana was described by Hall from the so-called Hamilton of 

 Clarksville, Mo., and the so-called Chemung of Burlington ; P. concent rim 

 only from the latter locality. It is probable that the rocks at all of these 

 localities are of nearly the same age. This being the case, the probabi'ity be- 

 comes strengthened that the three species first named are one and the same. 

 If so, P. concentrica, having been first published, will displace the other two 

 names. 



Peoducta semireticuxata, Fleming, (P. Martini, (De Kow) Win. Proc. 

 Acad. Nat. Sci. Phil. Jan. 1863, p. 4; figs. B. and Bb, Whittlesey, Proc. Amer. 

 Assoc. Cincinnati, p. 219.) This species occurs plentifully at Battle Creek, 

 Michigan. Collected by A. Winchell. Also in Hillsdale County. Collected 

 by Rev. J. D. Parker. 



A large specimen from the sands'ones at Burlington, Iowa, resembles, in 

 its want of mesial sinus, the forms of P. semireticulata occurring in the 

 Burlington limestone, rather than its associates in the same strata. It pos- 

 sesses in addition, a peculiar sharpness of the ribs not seen in oth r r speci 

 mens. 



Occurs also in Whittlesey's Collection from "Weymouth, Medina county. 

 Ohio, 60 feet below the conglomerate;" and " Sheldo 's sawmill, Orange. 

 Cuyahoga county, below the grindstone grit." 



P. Newberryi, Hall, (x. Rep N. Y. Regents, p. 180,) from Ohio, is perhaps 

 too closely related to this species. Dorsal valves cannot be distinguished- 

 from dorsal valves of P. semireticulata, as they occur at Battle Creek, Mich. 

 The ventral valve of P. Newberryi does not become so much arcuate, the con 

 centric wrinkling is a little more wavy, and less regular, the beak is less at- 

 tenuate, and projects less beyond the hinge, and the mesial depression is 

 smaller. 



Prodccta Cooperensis, Swallow, (Trans. St. Louis Acad. Nat. Sci. i. 640.) 

 The hinge line is shorter than in the typical specimens, but otherwise the 

 agreement is good. 



Bed "No. 1," Burlington, Iowa. " White Collection " of the University 

 of Michigan. 



Chonetes pulchella, Win., (Proc. Acad. Nat. Sci. Phila., Sept.. 1S62, p. 

 410). Collected by A. Winchell at Germain's and Alan's Quarries, Hillsdale, 

 Michigan. Oue specimen from this locality is larger than usual, presenting 

 a greater elongation of hinge line, which is drawn out at the extremities to 

 an abrupt acumination. The number of ribs is about 60. Two cardinal spines 

 are seen on each side of the beak, making an angle of about 60 with the 

 hinge line. 



Occurs also in Ohio, at " Howland, Trumbull County, one half mile east 

 from Center, at " Warren, Trumbull County, in coarse bedded sandstone, 

 next below the conglomerate," and at "Tallmadge, Summit County, in a boul- 

 der, supposed to be from the shales next below the conglomerate," Whittle- 

 sey's Collection. 



C. pulchella, in the number of its ribs, is. intermediate between C. Logani, 

 Nor. and Prat, and C. Illinoisensis, Worthen. In this character it most re- 

 sembles the former, while it differs from it in the smoothness of the ribs. It 



1865.] 



