JUKES-BROWNE : SYNOPSIS OF THE VENEEID^. 73 



particulars : they have smooth nymphs, a small angular sinus, and 

 the pedal scar is confluent with that of the adductor. 



Clausina, Brown, 1827. Type, Venus verrucosa, Linn. 



Shell oval or rotund, globose or compressed, with dominant 

 concentric structure. Lunule and escutcheon well defined, the latter 

 being unequally divided between the valves. Teeth less widely 

 divergent than in Periglypta, but normal, except that the anterior 

 lateral is small. Nymphs smooth. Pallial sinus always small and 

 angular. 



Clausina, s.s. Inflated and often globose, concentric ridges 

 crossed by irregular radial riblets which sometimes become nodular 

 prominences. Left anterior lateral very small and pustular ; right 

 laterals and pit often becoming obsolete. Pedal scar large, oval and 

 separate from adductor scar. 



Only a few species can be included in this group, viz., V. verrucosa, 

 Linn, (with the vars. canariensis and rosalina), V. nodulosa, Sow., 

 V. toreuma, (Jould, V. jukesi, Uesh., and V.fordi, Dall. 



Ventricola, Romer, 1857. Type, Vetius rigida, Dillw. ( — niqosa, 

 Chem.). 



Shell globose or merely convex, ornamented with numerous regular 

 concentric lamellae with striated interspaces and sometimes weak 

 radial striae on the posterior slope. Anterior denticle and its corre- 

 sponding pit both persistent. Pedal scar confluent or opening by 

 a channel into the adductor sear. 



This group includes V.casina, Linn., V. foveolala, Sow., V. ohlonga, 

 Hanley, V. declivts,^o\v., V. Igra, Sow., V.fffossa,V\n\., V. strigillina, 

 Dall, V. magdalena, Dall, V. rugatina, Heilprin (if not vars. of rigida). 



Circomphalus, Morch, 1853. Type, V. plicata, Gmel. (tixed by 

 Sacco, 1900). 



Shell compressed with flattened umbones, encircled by distinct 

 concentric lamellae which pass posteriorly into expanded elevations. 

 Hinge-plate much curved and attenuated posteriorly. Anterior 

 lateral very small and often impersistent ; pit in tlie right valve 

 obsolete. Pedal scar ratlier small, nearly separate, but connected 

 with the adductor scar by a narrow channel. Valve-margins very 

 finely crenate. 



The name Circomplialus was adopted by Morch from Klein, and 

 applied to the following small group of shells : V. peruviana, Sow., 

 V. dgsera, Linn. (= phcata, Gmel.), V. calophgUa, Phil., V. tiara, 

 Dillw., and V. berryi, (jray. In 1857 the Messrs. Adams also 

 ado|)ted it for the same group, and included many other species allied 

 to V. tiara, but without indicating any one as a type. In the same 

 year Romer proposed the name Anaitis fur what was practically the 

 same group, but this name was preoccupied by Duponchel in 1829, 

 and cannot therefore be used. 



No one seems to have selected a type for Circomphalus until 1900, 

 when Professor Sacco definitely indicated V. plicata. Gmelin, as the 

 type of a small group including V. lamellata and V. cahphylla, but 

 without giving any diagnosis, merely remarking that its members 

 were species which could not be referred to other sub-genera such as 



