142 JOURNAL OF CONCHOI.OGY, VOL. I4, NO. 5, JANUARY, I9I4. 



it fairly describes a majority of the species, though there are many 

 small variations, and a few considerable, even among the Helices, as 

 in Allogtiathus. The exceptions, however, are important — the aculeate 

 type, two arboreal types, and anomalous genera, like Brachypodella, 

 Physa, Gadinia, Afnphibola, and certain species of Ancylus. The 

 aculeate type is so called from the thorn-shaped teeth resting on a 

 base like the sole of a foot. In Iho. Agnathn all the teeth are aculeate, 

 though Varicella (a section of Glandina) has an obscure second cusp 

 — an important discovery we owe to the keen eyes of Mr. Hugh 

 Watson. Here is one link with the normal type ; and there may be 

 another in the variable central tooth of Circinaria. But the main 

 transition is found in Liinax, Nanina, Helicario?i, and their allies, 

 where the marginals only are aculeate. Yet. here, again, there is an 

 exception in the delicate teeth of slugs like Issele?iiia, Myotesia, and 

 Daviayantia, with Caldwellia and some species of Helicario7i. These 

 are all Eastern, ranging from the Philippines to Mauritius. 



One of the arboreal types is represented for the Old World by 

 A}iiphidronuis in Eastern Asia, by some species of Papuina . from 

 Papua to the New Hebrides, and by Chlorcea in the Philippines; and 

 in tropical America by Oxystyla, Ligiius, some species of BuHmuliis, 

 and many of Dryniceus. It is worth notice that Helicostyla in the 

 Philippines, Bulimiis (^Strophocheilus, Auris, Plekocheilus) and Xeno- 

 thauma in South America do not belong here. Speaking generally, 

 the central tooth is tricuspid, having a broad gouge-like central cusp, 

 and two small side cusps, while in the marginals — for there are no 

 laterals worth mention — the central cusp is as before, while the inner 

 lateral is suppressed. It will be seen that this is an easy modifica- 

 tion of the normal type. 



The other arboreal type is quite different in character and distri- 

 bution, being essentially Australasian. It comprises Janella and 

 Aneitea, Achatinella, Auriculella, and TornateUina. All these are 

 Polynesian, except that TornateUina reaches Mauritius in one direc- 

 tion, Juan Fernandez, and possibly South America in another. Here, 

 again, we have angulated rows and no laterals ; but the teeth are 

 clove-shaped and very numerous — the central generally with a median 

 denticle and two or three laterals ; the marginals on a similar plan, 

 but with the inner denticle the largest. This last is a point of strong 

 contrast to the Helicoid species generally, but I suspect this is a very 

 ancient type which must not be directly compared with the others. 



On the action of the radula I cannot say much, and indeed I do 

 not think it is yet fully understood, at least in the marine species. It 

 must be studied in life. There is a motion from front to back, and a 



