4 BULLETIN 192, UNITED STATES NATIONAL MUSEUM 



pectinated both upon its recurved edge and upon its main portion but 

 is not thereby separated by the pectinations into a group of individual 

 teeth. In a very few exceptions a mere indication of an additional minute 

 denticle is apparent on the rachidian and lateral tooth. There is no 

 jaw. The sole of the foot is longitudinally divided by a sulcus into two 

 muscular masses functioning independently from each other, thus giving 

 to the animal a method of progression by alternate waves of muscular 

 contraction, first on one side and then on the other. The foot is relatively 

 short. A bifid muzzle of varying length is always present. The tentacles 

 are long, slender, and fibrillar or slightly swollen at the ends. The eyes 

 are placed at the base of the tentacles on the outer side and are often 

 raised above the surface of the head by a fleshy protuberance. 



The operculum shows a wide degree of variation through the various 

 divisions of the family but follows, nevertheless, distinct lines of pro- 

 gression from a simple type to a very complicated structure, the steps 

 from one extreme to the other being easily traceable. All the opercula 

 possess a basal chondroid plate upon which calcareous ribs and lamellae 

 are placed, the modifications of which are used in subdividing the family 

 into a series of subfamilies and genera, as will be set forth below. Breath- 

 ing devices, slits, punctures, and siphons may be present or absent. 



The shell varies in shape from depressed-heUcoid to elongate-conic. 

 The sculpture varies from smooth to axially ribbed and spirally lirate, 

 the intensity of these sculptural elements varying from obsolete to lamel- 

 lose. 



Type genus : Annnlaria Schumacher. 



The family Annulariidae differs from the Pomatiasidae, an Old 

 World group, in the radula. The Pomatiasidae possess multicuspid rachid- 

 ian, lateral, and inner marginal teeth. The outer marginal is pectinated, 

 but the pectinations are confined to the reflected portion of the tooth. 

 In the Annulariidae, on the other hand, the rachidian and lateral teeth 

 are unicuspid, with a few exceptions where a small lateral denticle is 

 present, the inner marginal is multicuspid, and the outer marginal is 

 pectinate, but the pectinations extend beyond the reflected portion, in- 

 volving the main blade. 



The geographic range of the Annulariidae extends from the Bahamas 

 and lower Florida on the north, throughout the Greater and Lesser 

 Antilles and on the mainland from Mexico, to Bolivia. By far the great- 

 est development is centered in the Greater Antilles. 



KEY TO THE SUBFAMILIES FOUND IN HISPANIOLA 



Opercuhim without lamella or other reenforcements Chondropominae 



Operculum with lamella or other reenforcements. 



Operculum with obliquely curved ribs Rhytidopominae 



Operculum without obliquely curved ribs, with a single 

 calcified lamella Annulariinae 



