136 THE NAUTILUS. 



Micrarionta ; a group which should apparently be given generic 

 rank. Anatomically, Sonorella is not closely related to the Micra- 

 rionta series, which has its center in southern and Lower California, 

 and the adjacent border of Arizona. Data to be presented in our 

 forthcoming report on southwestern snails collected in 1906 and 

 1907 indicate that Sonorella, while remarkably varied in anatomy 

 specifically, yet shows no forms in any way connecting with the Cali- 

 fornian types of Helices. 



EXPLANATION OF FIGURES. 



Plate XI, figs. 6, 7, 8. M. desertorum. 



Fig. 9, genitalia of the same specimen; d. s., dart sack ; epi. t epi- 

 phallus ; _/?.. flagellum ; m. gl. t mucus glands ; p., penis ; sp. d., lower 

 portion of the duct of the spermatheca. The mucous glands and their 

 ducts are shaded. 



Fig. 10. Diagram of dart sack and mucous glands viewed from 

 the side towards the vagina, showing the contiguous insertions of the 

 mucous ducts. 



SOME NEW CALIFOENIAN SHELLS. 



BT WILLIAM HEALEY DALL. 



RISSOA (ALVANIA) GRIPPIANA Dall, n. sp. 



Shell small, brownish, solid, cancellate, with one and a half smooth 

 nuclear and five and a half sculptured whorls, nucleus flattish, 

 blunt, remaining whorls rotund, evenly enlarging ; last whorl with 

 13-14 axial ribs crossed by somewhat more slender, equal, equidis- 

 tant, spiral threads not tuberculate at the intersections, with three 

 somewhat stouter spirals on the base ; earlier whorls with two and 

 then three spiral threads between the sutures ; suture indistinct, 

 aperture obovate, rounded in front, slightly angular behind, with a 

 much thickened lip which in senile specimens is duplex at the mar- 

 gin. There is a very minute chink but no umbilicus. Length 8, 

 max. diam. 1.5 mm. 



Type specimens from Todos Santos Bay, Lower California, be- 

 tween tides, Hemphill, U. S. Nat. Mus. 46171 ; others from 12 

 fathoms sand, off the entrance to San Diego harbor, C. W. Gripp 5 



