CARBONIFEROUS FOSSILS. 11 



species, particularly that of the ventral valve. In the prominence of its beaks it 

 agrees more nearly with 0. MicfieUna, var. Burlingtonensis, Hall ; but it is a much 

 smaller shell, with a shorter hinge, and more rounded cardinal extremities. Mr. 

 Davidson, I understand, considers the form figured under the name 0. Michelina, 

 var. Burlingtonensis (after a careful comparison of authentic specimens), identical 

 with British examples of L'Eveille's species. This being the case, I cannot see 

 how the form under consideration can be distinguished from that species, unless 

 by its much smaller size. If the only two specimens I have seen are not young 

 shells, or accidentally dwarfed individuals, they may belong to a distinct species ; 

 but, until other specimens can be procured for comparison, I prefer to leave tho 

 question in regard to their relations to 0. Michelini for future consideration. 



GENUS PRODUCTUS, Sowerby. 

 PRODUCTUS SEMIRETICULATUS, Martin (sp.) 



PI. 2, Fig. 4, and 4 a. 



Anomites semireticulatus, Martin. Petrefact. Derb., pi. 32, figs. 1 and 2, and pi. 33, 



fig. 4. 1809. 



Anomites productus, Martin. Ibid., 22, figs. 1 and 2. 



Anomites Scoticus, Martini, and antiquatus, Sowerby. Min. Con. 1814 and 1821. 

 Anomites Martini and antiquatus, Phillip. Geol. Yorkshire, pi. 7, fig. 2. 1836. 

 Leptcena antiquata and tribulifera, Fischer. Oryct. Mosc., pi. 26, figs. 4 and 5, 



and pi. 26, fig. 1. 1837. 



Productus Martini, De Koninck. An. Foss., pi. 7, fig. 2. 



Productus Inca and Peruvianus, d'Orbigny. Voy. Am. Mer., pi. 4, figs. 1, 3> and 4. 

 Productus flexistriata, McCoy. Synopsis Carb. Foss., Ireland, pi. 17, fig. 1. 1844. 

 Productus semireticulatus, De Koninck. Monogr. Gen. Product, pi. 8, fig. 1. 

 Productus Calhounianus, Swallow? Trans. St. Louis Acad. Sci., vol. 1, p. 215. 



1858. 



THE specimens of the shell referred to the above-cited species are very imper 

 fect, but seem to agree in all their visible characters with that well-known form. 

 Still it is possible that better specimens, showing the entire shell and its internal 

 characters, might present differences warranting its separation. It evidently 

 attained a large size, some of the specimens indicating a transverse diameter of 

 near three and a quarter inches. 



