Achatinella and other PalmoncUa. 335 



terrestrial habits of tlie animals, is evidently faulty, seeing 

 that, irrespective of such characters and habits, the Achciti- 

 nellce, dentition considered, may be very properly divided 

 into two, perhaps three, subgenera, alike embracing forms 

 comprised in each of Gulick's groups. 

 The details of anatomy here follow.* 



In Laminella Mastersi the jaw is low, wide, slightly arcuate, ends but 

 little attenuated, blunt; it is of horn color, thickest on the cutting edge, 

 gradually thinning off to the upper margin. There is no median projec- 

 tion to the cutting edge. The anterior surface is without ribs. Of ithe 

 same type is the jaw in all the species of Laminella examined It is very 

 wide, very low, and hardly arcuate in luctuosa. I find the same type of jaw 

 also, though much more arched, in all the species of Neivcombia and Lepta- 

 chatina examined. In picta there is a slightly produced, blunt, median 

 projection to the cutting edge. All these species have jaws readily boiled 

 out by caustic potash, and usually remaining attached to the lingual mem- 

 brane in the test tube after the process. There are delicate vertical striae 

 on several of them, sometimes shown only by a very strong power. In 

 all the other species submitted to me the jaw is so extremely delicate as 

 to be found with difficulty. I failed to extract it in Achatinella Johnsonii, 

 livida and varia.f In the other species of Achatinella, and in all of Far- 

 tulina, the jaw appears to be simply arcuate, transparent, extremely thin, 

 ends blunt. 



The lingual membrane is of the same type as figured for Fartulina huli- 

 moides by Heynemann (Mai. Blatt. XIV), in all the species of Achatinella 

 s. s., and Partulina. It is very broad in comparison to its length. In 

 one specimen the formula is 175-1-175. J The teeth are arranged en chev- 

 ron. There is but one type of teeth for centrals, laterals and marginals, 

 the former being, however, somewhat smaller, and symmetrical The 

 teeth are long, narrow, bluntly truncated below, curving and widening at 

 first gradually, then more rapidly, so that the apex is more than twice the 

 breadth of the base; it is reflected along its Avhole breadth, slightly pro- 

 duced, seven-cuspid, the central cusp the smallest. There is variation in 

 these cusps. 



In Ketccomhia, Laminella :Mid Leptachatina Juha lingual membrane is en- 

 tirely different. It is as usual in the Helicinoe, narrow compared with its 

 length, the teeth arranged in horizontal rows. The centrals are long 

 narrow, somewhat wider at base (where there are two long, parallel, 



* I alone am responsible for these an.itomical details.— W. G. B. 



t The ]irocess of extraction by potash is not adapted to this slightly developed j.tw; 

 even by dissection it is very difficult to obtain the jaw ; when mounted in glj-cerine jelly 

 it speedily becomes too transparent to be studied under the microscope. 



X Counted by my young friend A. Ten Eyek Lansing, to whom I am indebted for val- 

 uable aid in dissecting the specimens. 



