MUSEUM OF COMPARATIVE ZOOLOGY. 321 



This interesting species should be studied with a large series, for individual 

 specimens of the varieties above referred to it would seem sufficiently distinct 

 for specific rank, in the absence of the connecting links. The shell, as originally 

 described by Forbes, Philippi, &c, is small, slender, and very obliquely twisted. 

 It is characterized by a spiral sculpture of flattened delicately vesicular threads, 

 by two revolving ridges, and by ix-xv transverse ribs. In the typical hel- 

 lenica the ridges are obsolete, the ribs rather strong, weakest on the periphery, 

 with pits between their extremities at the suture. There are usually a few 

 ribs, irregularly distributed, which are larger and more varicose than the 

 others. 



In the variety pumilio (subvaricosa Dkr., non Cantraine), the anterior re- 

 volving ridge is basal, the posterior forms a peripheral carina; the ribs have 

 disappeared, leaving only nodules on the two ridges and at the suture; there 

 is at most one extra varix, and usually none. 



The variety scceva Mbrch differs from the typical hellenica in its larger size, 

 the more oblique ribs, strongest on the periphery, the absence of the revolving 

 ridges, especially the anterior one, and the greater prominence of the extra 

 varices. It is proportionately stouter, and the sutural pits are smaller and 

 more numerous, even nearly obsolete at times. 



In the variety nodosocarinata the ridges are strong, as in var. pumilio, but 

 both are more posterior, and the ribs in the intervening space are strong, regu- 

 lar, and oblique. In size this variety is between pumilio and scceva. There 

 are usually no extra varices. 



In what I suppose to be variety Lccana of Verrill, but of which I have not 

 seen adult and perfect examples, the ridges are obsolete, the ribs more nearly 

 axial in direction and rather irregular in breadth, stronger on the periphery 

 in the last whorl only ; the sutural line irregular and not foveolate, the extra 

 varices numerous, sometimes one to each whorl, the spiral threads rather finer 

 than in var. scceva. The shell is somewhat larger, and, as might be expected 

 from its northern habitat, less porcellanous and more earthly in color than 

 southern varieties. All the varieties have a smooth shining subcylindric 

 nucleus, which is generally brownish, or if light colored has a brownish line 

 near the suture. 



In the variety Morchiana the shell is more slender; the ribs are fewer, stronger 

 at the periphery, obsolete at the sutures, which are regular, and form an even 

 spiral without pits, the whorl in front of them being evenly marginated; there 

 are no revolving ridges nor basal carina; the spiral sculpture is as in var. 

 •pumilio. 



In the variety bicarinata the carina; are present and very strong, but not 

 nodose on the last whorl ; from the figure the ribs would seem to be wholly 

 absent, but the suture is conspicuously punctate. Reeve's figure in the Iconica 

 looks as if the type was a worn or beach specimen. 



VOL. XVIII. 21 



