248 AMERICAN JOURNAL 



papillose, infra-anal orifice bifid, to right of anal, on a l)ro:ul, 

 not prominent swelling. Renal orifice round, minute, hardly 

 elevated, some distance to the left of the anal papilla. Tiie 

 length and stoutness of tentacles differ in different individuals. 

 Some varieties approach very closely to the black variety of 

 (J. scahra. 



Var. Cummgii, (Rve.) 



Shell elevated, compressed, with a narrow black or slightly 

 spotted border; externally black, with small bluish white spots 

 radiating from the apex and becoming elongated into stripes 

 near the margin, in some individuals ; quite or almost destitute 

 of radiating strige. 



Soft parts : foot oval, elongated, smooth, light yellowish, sides 

 a little brown, extreme edge thin, crenate (in alcohol). Thick- 

 ened mantle-edge smooth, broad, very finely crennlate on ex- 

 treme edge, with a single row of very fine white cilia ; hood 

 longer than in normal variety, very varicose ; head prominent, 

 light brownish, stout; muzzle stout, transversely rounded; fringe 

 broad, striate, even, somewhat crumpled ; disk radiately striate, 

 bordered with a double row of granulose tubercles, the inner 

 row most prominent; mouth subcircular, somewhat pointed be- 

 low ; tentacles as in normal variety. In most specimens, in 

 alcohol, of this and other species, several impressed longitudinal 

 lines may be noticed, perhaps due to the contraction caused by 

 the preservative ; gill moderate, rather longer and narrower 

 than in normal variety ; anal and infra-anal papillje close to- 

 gether at the extreme right, less prominent, but otherwise as in 

 variety normalis. Renal orifice minute, rounded, inconspicuous, 

 midway between the gill on the left hand side and the anal 

 tubercle on the right. Radula, as usual in the Acmmdcf, in two 

 long double loops on the upper surface of the liver. Formula 

 as in the last. 



This variety, if it were not so closely connected by hybrids 

 and intermediate forms with the other, would undoubtably rank 

 as a distinct species. It is a northern form and the northern 

 specimens are uniform and remarkably distinct from the southern 

 pintadina. They become inextricably mingled, however, about 

 Sitka, and puzzle the student beyond description. It seems as 

 if several distinct local forms had spread, and at the points of 

 meeting had hybridized until the hybrids and varieties equalled 

 or outnumbered those wliich adhered to the original types ; 

 rather than that all had a common origin in one type. Further 

 researches among the Aleutian Islands and on the east coast of 

 Asia, are necessary, before we can trace the development of 

 these forms, with any satisfaction. 



