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TERTIARY FAUNA OF FLORIDA 



burrow probably attract many infusoria and other minute organisms which 

 serve as food for the bivalve. Such burrows are known to be frequented by 

 various commensal Leptonacea. Stoliczka supposed that it would be neces- 

 sary to remove Hindsiella from the vicinity of the Erycinida on account of its 

 external ligament. But the fact is that ligament and resilium are both repre- 

 sented in a majority of the Leptonacea, sometimes one is obsolete and some- 

 times the other, but it is doubtful whether either is absolutely deficient in any 

 case. A careful examination of the hinge of H. arcuata leads to the belief 

 that the ligament of this type was not, as Deshayes supposed, entirely external. 

 At all events, from all the facts, it does not seem that a sufficient reason has 

 been advanced for separating this group from the Leptonacea. As Smith 

 has already shown, a variety of forms have been referred to these groups solely 

 on account of their external form. The type of Hindsiella has in the right 

 valve a single small conical tooth under the umbo, behind which the hinge- 

 plate is wide, somewhat excavated, and exhibits what appears to be an elon- 

 gated thickening upon which the resiliary part of the ligament was seated. 

 In the left valve the hinge is similar, but there is a second small tooth behind 

 the more prominent one in front of the resilium, the resiliary process is less 

 prominent, and a distinct groove may be seen where the posterior part of the 

 external ligament terminated. The ligament and resilium were in contact, 

 but both were present. It is difficult to decide whether the elongate posterior 

 lamina is a " tooth" or a resiliifer. Whichever is the case, it appears in the 

 American species also. I am indebted to M. Cossmann for the opportunity 

 of studying authentic valves of this curious little shell. 



Deshayes's name being preoccupied, Stoliczka modified it to Hindsiella, 

 while, a short time after, Fischer, apparently ignorant of Stoliczka's action, 

 proposed Vasconia for the same reason. As he specifically states this, it is 

 not practicable to use his name for a curious little shell described at the same 

 time by Fischer as Hindsia Jeffreysiana, and which is separated from Hind- 

 siella by good characters. The latter is a purely external shell, usually with 

 a distinct unpolished periostracum, and the sinuosity in its base is merely a 

 sinuosity without distinct boundaries. The H. Jeffreysiana, however, is a shell 

 almost entirely if not wholly internal, without an epidermis, with a solely 

 internal, small, short, subumbonal resilium and no external ligament; the 

 sulcus in the valves is a sharp slit, leaving a fascicle with sharply defined 

 boundaries, and the cardinal tooth, unlike those of Hindsiella, though similarly 

 placed, is clean cut and sharp. These differences obviously correspond to 

 serious anatomical characteristics of which Hindsiella. has no trace in its shell. 



