560 PROCEEDINGS OF THE ACADEMY OF [DeC, 



ON THE TEETH OF HAWAIIAN SPECIES OF HELICINA. 



BY HENRY" A. PILSBRY AND C. MONTAGUE COOKE. 



The dentition has been examined in four Hawaiian species of Heli- 

 cina: H. haldwini Anc, H. uherta Gld., H. laciniosa Migh. and H. 

 rotelloidea Migh. The chief divergence is in the denticulation of the 

 fourth or major lateral tooth, which is armed with several large and 

 small denticles in some species, and with more numerous equal denti- 

 cles in others. 



Helicina baldwini. Fig. 2.— Helicina laciniosa. 



In all the species, the central tooth has a very short smooth cusp or 

 ledge at its summit. 



In H. baldwini (fig. 1) the denticle formula of the laterals is 6, 5, 4, 

 5, 0; that is, the innermost lateral tooth has 6 points or denticles on 

 its recurved cusp, the next tooth has 5, and so on. The inner 

 uncini have three or four rather large denticles. Lateral iv has very 

 vmequal conic denticles, two of them much larger than the others. 



H. uherta is like haldwini, except that the inner lateral has only 4 

 denticles. 



H. laciniosa (fig. 2) has the denticle formula 5, 6, 4, 7, 0. The 

 major lateral (iv) has an even series of subequal denticles. The 

 inner uncini have about 7 very minute, subequal denticles. 



The radula of H. rotelloidea resembles that of H. laciniosa, the 

 major lateral having 6 subequal denticles, but the inner uncini are more 

 like the H. haldwini type, having about 4 large denticles. What 

 systematic value attaches to the differences observed is uncertain until 

 many more species can be examined ; but it would seem that two groups 

 are indicated, characterized by the mode of denticulation of the cusp 

 of the fourth lateral tooth. 



The figures represent the central (c) and lateral teeth (I'-r), with a 

 single uncinus (w). 



