240 INVERTEBRATA OF MASSACHUSETTS. 



Of the five specimens I have examined, three were mature, and two 

 young. In the oldest, the width of the shell is proportionally greater, 

 and there is a tendency to angularity at about the upper fourth of the 

 last whorl. 



GENUS JANTHINA, LAM. 



Shell sub-globose, thin, fragile, spire short ; aperture angular 

 at the anterior junction of the inner and outer lips ; pillar twisted ; 

 lip thin, with a sinus at the middle. 



JANTHINA FRAGILIS. 



Shell thin, brittle, conical, ventricose, violaceous beneath, whiter 

 on the spire. 



State Coll., No. 292. Soc. Cab., No. 942. 



Helix janthina, LIN.; GMELIN ; Syst., 3645, No. 103. LISTER; ConcA., t. 572, 

 f. 24. RUMPHIUS; Mus., t. 20, f. 2. GUALT. ; Test., t. 64, f. O. SLOANE ; 

 Jamaica, t. 1, f. 4. BROWN; Jamaica, t. 39, f. 2. D'ARGENV. ; Conch., pi. 6, 

 f. 5. CHEMN. ; Conch., v. t. 166, f. 1577, 1578. WOOD ; Index, pi. 34, t. 116. 



Janthina fragilis, BRUG. ; Encyc. Mtth, pi. 456, f. 1. Ann. du Mus., xi. 123 

 (animal). BLAINV. ; MalacoL, pi. 37 bis., f. 1 a. SOWERBY ; Conch. Man., 

 f. 333. 



Janthina communis, LAM. ; An. sans Vert., (1st. ed.) vi. 206. 



Shell globose-conic, thin, brittle, transparent ; whorls three or 

 four, forming a short spire, the last one very large, and angular at 

 the middle ; beneath the angle the color is deep violet, lighter 

 about the axis, and above it the color is merely tinted with violet, 

 a little darker at the suture ; surface shining, wrinkled by the lines 

 of growth, and with short, oblique wrinkles above the angle of 

 the last whorl, and marked with revolving lines beneath that angle ; 

 aperture large, semi-oval, outer lip very thin, retiring as it passes 

 the angle of the whorl, so as to produce a shallow recess ; inner 

 lip cylindrical, straight, corresponding with the axis of the shell. 

 Length T \ inch, breadth 1 inch. 



The Janthina floats, by means of a mass of vesicles, at the 

 surface, throughout the wide ocean, and is not unfrequently driven 

 upon the ocean shores by storms. After a severe gale, in the 



