468 PROCEEDINGS OF THE ACADEMY OF [1890. 



indicate the identity of the formation which covers, or at one time 

 covered, the greater part of the Republic : 



Hippurites Mexicana. — States of Mexico, Queretaro, Hidalgo, San Luis Potosi, 



Coahuila, Vera Cruz, Puebla, Guerero, Morelos. 

 Hippurites calamitiformis. — Mexico, Queretaro, Vera Cruz, Puebla, Morelos, 



Michoacan, 

 Radiolites Mendozae. — Queretaro, San Luis Potosi, Vera Cruz, Guerero, Michoacan. 

 Nerinaea Castilli. — Queretaro, Hidalgo, Vera Cruz, Morelos, Michoacan. 

 Nerinaea Barcenae (N. hieroglyphica, of Biircena). — Vera Cruz, Guerero, Michoacan. 

 Enallaster Mexicanus. — Chihuahua, Colima. 



I have little doubt that some of the species above enumerated are 

 found in States other than those mentioned, but the distribution as 

 given sufficiently illustrates the broad range of the species. 



Plates XII-XIV illustrate the forms which I myself found in the 

 limestones and marbles of the Cerro de Escamela, near the town of 

 Orizaba. Some of these are clearly identical with the species which 

 Barcena first described in his " Datos para el Estudio de las Rocas 

 Mesozoicas," but I have thought well to figure them, together with 

 the other unnamed and less recognizable forms, so that they might 

 more readily serve the wants of the^paleontological student. 

 Nerinaea Castilli. (PI. XII, fig. 1). 



The fragment of this species, as shown on a polished surface of 

 marble, measures three and a half inches in length ; what the total . 

 length of the shell may have been I am unable to say, but it doubt- 

 less considerably exceeded half a foot. The species, which Barcena 

 has minutely described, seems to be well defined from any of its 

 European congeners. 

 Nerinaea Barcenae. (Plate XIII, figs. 3 and 4). 



This is the form which Barcena doubtfully identifies with N, 

 hieroglyphica, supposed to represent the European Jurassic formation. 

 I have in vain searched for a recognized species of that name, nor 

 have I been able to find a species, either Jurassic or Cretaceous, 

 which agrees in its columellar features with the Mexican fossil. 

 With the strong probability that the identification with a Jurassic 

 form is erroneous, I have thought it best to rename the species, and 

 in doing so take pleasure in recalling the name of the distinguished 

 Mexican geologist, Mariano Barcena. 

 Nerinaea sp. ? (PI. XIII, fig. 6). 



The form here represented is likely to be a deeper section of the 

 last-named, or_ it may be the form which Barcena doubtfully 



