FREE INSTITUTE OF SCIENCE 



805 



TERTIARY FAUNA OF FLORIDA 



" Lauatiis." By some confusion of this with IVIontfort's Lanistes (which is 

 cited by Swainson, p. 387, as Lanitcs) this error probably arose. 



I have not access to Dieffenbach's New Zealand at this writing, but if the 

 Modiolacra cited from it by Ilutton is correct, it is probably a typographical 

 error for Modiolaria, and. an earlier citation of Beck's name than is usually 

 known. 



This genus is distinguished from Crcuclla by its elongated siphons, the 

 branchial one being usually shorter and not closed along its lower side, but 

 merely with apposited free edges ; the foot also differs, being long and taper- 

 ing to a point, instead of clavate as in Croiclla. It is somewhat difficult to 

 apportion the fossil species, but they are perhaps best separated from Crenclla 

 by the impressed mid-lateral area which, in the typical Modiolaria, is usually 

 smooth or not radially sculptured. 



The genus may be divided as follows : 



Modiolaria s. s. Shell with three areas on the disk, the central with feeble or 

 entirely without radial sculpture, the others radially sculptured. Branchial 

 siphon considerably shorter than the anal. Type Mytihis discors L. = 

 M. discrepajis Mont. 



Lioberus Dall. Shell with the radial sculpture obsolete or absent; branchial 

 siphon equal or nearly equal to the anal, both much elongated. Type 

 Modiola castanea Say, Journ. Acad. Nat. Sci. Phila., ii., 266, 1822.* 



Rlioniboidella Monterosato (1884). Shell rhomboid, the surface entirely 

 covered with sharp radial striations. Type Modiola. rhombea Berkeley. 



? Planimodiola Cossmann (1887). Shell modioliform rather than rhomboid, 

 with the anterior radiated area very small and the valves rather com- 

 pressed. Type Modiola sidcata Lam. (Parisian Eocene.) 



This section might quite as well be placed in Modiolus, from which it 

 differs by no very important characters. It is very doubtful if it is a Modiolaria. 

 The type is not the same as the recent Modiola stdcata of Lamarck (= M. 

 {Brachydentes) citrimis Bolten). 



The earliest species in our Tertiary is probably M. snbpontis Harris, from 

 the Upper Midway, though its generic position is not positively determined. 



* This is probably the same as M. lignea Reeve, Conch. Icon., x., Modiola, pi. 10, fig. 71, 185S. 

 M. castanea Say was mislakenly referred by Tryon to the young of M. tttlipa Lam. in Am. Mar. 

 Conch., p. 187, 1874. 



