688 PROCEEDINGS OF THE ACADEMY OF [DeC, 



THE ANATOMY OF TWO BRAZILIAN LAND SHELLS, ANOSTOMA 

 DEPRESSITM AND TOMIGERUS CLAUSUS. 



BY HAROLD HEATH. 



Among the many strange species of Brazilian land shells, those 

 belonging to the genus Anostoma and Tomigerus present the most 

 unusual characters. In the first named the last whorl of the shell 

 is "straightened, turning toward the margin and upward" (Pilsbry^), 

 so that the visceral mass is carried upside down. Pilsbry has sug- 

 gested that, judging by the growth lines, the shell is carried at first 

 with the equatorial plane nearly vertical, and that as the last whorl 

 is being added the animal falls to the right, thus undergoing a twist- 

 ing process which brings the spire of the shell into a reversed position. 

 Unfortunately, no young, living individuals were secured by the 

 Stanford Expedition, but in the shell (PI. XXXI, figs. 2, 4) of one imma- 

 ture specimen the free borders are highly angular, and if held in an 

 upright position, as Pilsbry suggests, would offer the least possible 

 resistance in moving about through the grassy regions where these 

 snails abound. 



The specimens of Anostoma on which this paper is based were found 

 in the low hilly country in the neighborhood of Baixa Verde, a small 

 settlement between 40 and 50 kilometers to the northwest of Natal. 

 A fire had swept the region in comparatively recent times, and 

 fragments of shells were everywhere abundant in the scrubby under- 

 brush of the rocky hills. Extended search brought to light a single 

 living individual in a profound state of sestivation, Avhich a prolonged 

 stay in a moist chamber failed to terminate. In addition, five dead 

 shells were discovered in a heap of stones, and were measured and 

 described in the field. According to my notes made at the time, 

 they vary in greatest diameter from 33 to 37 mm. ; in lesser diameter 

 from 24.5 to 28.5 mm.; and in altitude from 16 to 17.5 mm. Also 

 in regard to the number and position of the apertural teeth or lamella? 

 there is considerable variation. In two specimens there are seven, 

 two of them being parietal ; in another there are likewise two parietal 

 folds, but the columellar lamella is absent; in the remaining two 

 there are three parietal folds, the middle one curving behind the 



1 Manual of Conchology, Vol. XIV. 



