44 PROCEEDINGS OF THE ACADEMY OF [Vol. LXXIV 



? Subglobulosa A. J. W. (1905). " Tvpe (by tautonomy) H. subglobulosa Poey 

 L852 Cuba. 

 O. orbiculata orbiculata Say (1818). Mouth St. Johns R., Fla. (s. U. S.). 

 ?? //. ambeliaw Sowerby (1842). 

 ?? //. yestffa "Guild." Sowerby (1842). X. A. Young shell; might be any 



helicinid. 

 H. hanleyana Pfr. (1849). New Orleans, La., U. S. 

 #. snhnrlnfu.lt, i and #. subtropica appear to be Ms. names. 

 O. orbiculata tropica ("Jan" Pfr.) (1850).Tampico, Mex. (and s. w. U. S. ). 

 O. orbiculata clappi (Pilsbry) (1909). Central and Eastern Fla. 

 VO. borealis (von Martens) (1890). Villa Lerdo, Durango, Mex. 



O. cordillerae ("Salle"Pfr.) (1857). 3500 meters, Mt. Orizaba, V. C. Mex. 

 O. convexa (Pfr.) (1849). Bermuda Islands. 



In this typical section, the radula of the type species, 5 and that 

 of 0. convexa* have been examined. The radular formulae are 

 given in Table II. The centrals of 0. orbiculata (Plate III, fig. 2) 

 are similar to those of Hendersonia, but the R-central has a less 

 attenuate base, and the C-central has considerably smaller cusps. 

 The comb-lateral is somewhat lighter, while the accessory plate 

 is both lighter and much more elongate transversely (Plate IV, 

 fig. 11). The wing is somewhat reduced, and gives a lanceolate 

 outline. The marginals are very close to those of Hendersonia, 

 but are slightly more numerous. 



The radula of 0. convexa is not figured, but it is very close to 

 that of 0. orbiculata. The formula is given in Table II. The 

 shell of 0. convexa is also very similar to that of 0. orbiculata; it 

 is of the same depressed form and has a similarly thickened peris- 

 tome. In this connection, a number of Antillean species, included 

 by A. J. Wagner in the sections Subglobulosa and F estiva, need 

 examination. Many of them have the calcareous, light-colored 

 opercula of this group. 



This group has many primitive characters, but in the reduction 

 of the wing on the accessory plate, slightly approaches Oxyrhombus 

 of Helicina. Its closest relatives are in the section Succincta, thru 

 which it is connected with Alcadia. As indicated in the relation- 

 ship diagram in Table I, it probably represents a primitive stock 

 near the ancestral line of the genus Helicina. The distribution 

 of the species appears to sustain this idea, If the Antillean species 



1 < (roups preceded by a question-mark are those of which I have not examined 

 the radula; species preceded by a question-mark are those I have not seen; 

 in the latter, 2 question-marks indicate considerable doubt as to its position 

 or specific rank. 



5 alcoholic specimens; A. X. S. P. no. 91705; collected near Frierson, La., 

 by l>. S. Frierson I L906). 



alcoholic specimens; A. X. S. V. no. X5558; collected on flats near Frascati 

 Hotel, Bermuda, by A. Gulick (1903). 



