1922] NATURAL SCIENCES OF PHILADELPHIA. 47 



Leialcadia A. J. Wagner (1907). Type (now chosen, as used by author as 



Idesa) H. rotunda d. Orbigny (1845). 

 Nitida A. J. W. (1907). Type (by tautonomy) II . nitida Pfr. (1839). 



Cuba. 

 Megastoma A. J. W. (1907). Type (by tautonomy) H. megastoma C. B. 



Adams (1849) Jamaica. Not Megastoma Morris and Lycett (1850), 



Costa (1850), nor Swainson (1837). 

 Mamilla A. J. Wagner (1907). Type (by tautonomy) A. mammilla 



Weinland (1862) (A. mamilla A. J. W.). Not Mamilla Tryson (1883), 



emendation of Mammilla Schumacher (1817). 

 ? Bellula A. J. Wagner (1907). Type H. bellula "Gund." Pfr. (1859) 



Cuba. 

 ? Ampliata A. J. Wagner(1907). Type H. ampliata C. B. Adams (1850). 



Jamaica. 13 



Section Analcadia A. J. W. Antilles to Central America. 



Analcadia A. J. W. (1907). Type (now chosen) H. dysoni Pfr. 

 (1849). Cumana, Venezuela. 



?0. dysoni bocourti (C. and F.) (1869). Belize, Honduras. 



??0. dysoni diaphana (Pfr.) (1851). Honduras (small, angulate form). 



?H. dysoni jasoni von Martens (1890). Isle Bonacca, Honduras. 

 ???0. sanguinea (Pfr.) (1849). Honduras (Dyson). Probably an Antillean species. 



In this subgenus the radulae of C. palliata u , O. rotunda 15 , and 

 O. riparia (Pfr.) 16 were examined. All are included in Table II, 

 but only 0. palliata is figured (Plate V, fig. 25) here. The differences 

 are indicated in the synoptic key, and in Table II. Except for 

 the broad R-central of O. dysoni, they differ mainly in size. 



From the indications given by these few radulae, Alcadia appears 

 very close to Oligyra s. s. A. J. Wagner (1907) has shown in his 

 study of the opercula and shell characters, that the Mexican species, 

 which he groups around O. gemma, are connected, in these parti- 

 culars, by an intergrading series with the typical forms of Alcadia. 

 In the radulae, the biggest break comes between the West Indian 

 forms and those of the mainland (exclusive of Analcadia). Never- 

 theless, the whole group of radulae, included here in the genus 

 Oligyra, form a very closely related group, separated from other 

 genera by quite distinctive characters. It is true that the subgenus 

 Alcadia and the subgenus Oligyra appear to represent the basal 

 members of two diverging lines of evolution, but at present it 

 would be extremely difficult to name any very definite characters 

 for their separation. 



13 The last two sectional names can be used. 



14 2 dried specimens; A. N. S. P. no. 101204; collected at Somerset, Manchester, 

 Jamaica by A. P. Brown (1910). 



15 1 dried specimen; A. N. S. P. no. 77022; collected at Marianao, near Havana, 

 Cuba, by S. N. Rhoads (1899). 



16 2 alcoholic specimens; collected for Univ. of Mich. Museum, near La Fria, 

 Estado Tachira, Venezuela (1920). 



