54 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 58. 



ANNULARIIDAE, new family. 



This family includes all the New World ''Cyclostomoid" mollusks 

 placed under the family name of C^^clostomatidac or Ericiidae. 



The chief distinguishing character which separates this group from 

 all other operculate pulmonates is found in the radula which funda- 

 mentally is uniform throughout the large number of species, which 

 are included. The radula possesses a unicuspid rachidian tooth; 

 a single unicuspid lateral tooth, and two marginals — the inner one 

 resembling in form the lateral tooth but multicuspid — and an outer 

 one which is long and curved like a bow and is pectinated both upon 

 its recurved edge and upon its main portion, but is not thereby sepa- 

 rated by the pectinations into a group of individual teeth. There is 

 no jaw. The sole of the foot is longitudinally divided by a sulcus 

 which separates it into two muscular masses functioning inde- 

 pendentl}' one of the other, and 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 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 

 progression 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 sub- 

 dividing the family into a series of subfamilies, and genera, as will 

 be set forth below. 



The shell varies in shape from depressed helicoid to elongate conic. 

 The sculpture varies from axially ribbed only to axially ribbed and 

 spirally lirate, the intensity of these sculptural elements varying 

 from obsolete to lamellose. 



Type genus. — Annularia Schumacher. 



The Annulariidae differs from the Ericiidae, an Old World group, 

 in the radula. The Ericiidae possess multicuspid rachidian, 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 always unicuspid, the inner marginal is multicuspid, and the 

 outer marginal is pectinate, but the pectinations extend beyond the 

 reflected portion, involving the main blade. 



These radular differences have long since been cited by authors. 

 There is an error on the part of Troschel (Das Gebiss der Schnecken, 



