410 Mr. W. H. Benson on Ianthina, Bolten. 



increasing whorls of the true species. The chief character of the 

 u discoid • /. planispirata consists, according to the original de- 

 scription, in "its narrow depressed mode of convolution," of 

 which Reeve's figure No. 9 exhibits no appearance, the body of 

 the shell in the latter exceeding in magnitude the area of the 

 aperture, whereas in the ' Samarang' figure the aperture is larger 

 than the body of the shell. Morch refers Reeve's figure to I. 

 planispirata as " var. 7. grandis," without further remark. 



A. Adams says nothing of the sculpture. All my specimens 

 are sculptured with undulate and radiate striae, which are more 

 closely packed and more sharply plicate on the basal portion. 

 Morch refers /. planispirata to the subgenus lodes, Leach, the 

 animal of which is stated to be viviparous. 



/. fragilis, Lam. (including the variety I. affinis, Reeve). 



The violet colour of the under side of the shell was visible in 

 the water through the float, and assisted to distinguish it from 

 the foam. The float was of strong texture, and was composed of 

 large transverse polyhedrous globules arranged in a convex form 

 on the surface exposed to the air ; one proved to be dichotomous, 

 evidently from some accident. The cilia within the animal's 

 mouth were stiff and prickly. Morch includes the species in 

 the subgenus Achates, Gistel, recorded as being oviparous. Our 

 specimens were destitute of ovisacs ; whether in consequence of 

 the season for their reaching maturity having passed, and of the 

 animals having provided themselves with fresh floats, or from 

 their being permanently deficient in those appendages, cannot 

 be asserted. As soon as the water in which the specimens were 

 placed for examination was changed, a quantity of beautiful car- 

 mine fluid ejected spoiled it, and all died on the following day, 

 some of them casting off their shells, when the animal, including 

 the spiral portion, remained attached to the float at the surface 

 of the water. A gummy coat, which was easily rubbed off while 

 the shell was wet, dried into a moderately polished surface. 



The dimensions of four examples are as follow, tending to 

 corroborate Morch' s suggestion regarding /. affinis, Reeve : — 



Specimen resembling I. affinis 

 Approximate form .... 

 Depressed variety .... 

 Smallest specimen .... 



The last approaches in form Rang's figure, which Morch refers, 

 as a variety, to 7. violacea, Bolten. 



Respecting the younger examples of the variety taken in the 

 Bay of Bengal, I only noted the number of individuals captured. 



