8 THE NAUTILUS. 



clear that the lines, when present, are incised. As the sculpture 

 increases in strength, the intervals between the incised lines dimin- 

 ish, and when they become equal, the surface becomes typically 

 striate and the revolving sculpture consists of incised or elevated 

 lines, as the observer chooses to designate it. 



Very rarely the surface is distinctly malleated, in which case there 

 is a series of irregular, raised, revolving lines, which are quite differ- 

 ent from the regular sculpture of var. striatus. The intensification 

 of the spiral sculpture characteristic of this form seems to be peculiar 

 to the northern states, as it has not been noticed from south of Mason 

 and Dixon's Line. The most characteristic specimens come from 

 the northern tier of states from Maine to Michigan. 



The types were pleistocene fossils from Milwaukee, Wisconsin. 

 It is a common form in Michigan, varying in size and proportion 

 like typical bicarinatus. Specimens are also before me from the 

 following localities: Square Lake; Rockville, Me.; Profile Lake, 

 N. H.; Cedar Lake, N. Y.; Port Oram, N. J.; Gore's Bay, Mani- 

 tolin, Id., Lake Huron, Algoma; Georgian Bay, Ontario. 



VII. Var. PORTAGENSis Baker, pi. I, fig. 9. 



Planorhii bicarinatus portagensis Baker, Naut. XXII, p. 45 (1 908). 



This recently described and very striking form is characterized by 

 its closely coiled whorls, deeply funicular upper and lower surfaces 

 and acute carination; the umbilicus is comparatively narrow and 

 deeply excavated; the aperture is large, auriculate, higher than wide, 

 and acutely angled above and before; the lip is sharp and but slightly 

 expanded. 



Type locality. Portage Lake, Aroostook Co., Maine. Also Square 

 Lake, Cross Lake and Second Lake, Aroostook Co., Me. (Walker); 

 Meaches Lake, Hull, Quebec (Pils.). 



The figure is drawn from a cotype kindly furnished by Mr. F. C. 

 Baker. Specimens from Carp Lake, Emmet Co., and Betsey Lake, 

 Benzie Co., Michigan, though not typical, may fairly be referred to 

 this form. Immature examples, especially those from Betsey Lake, 

 are almost identical with tlie immature Maine specimens, the whorls, 

 perhaps, being more regularly rounded and lacking the decided flat- 

 tening towards the base of the typical form. But the mature shells, 

 though retaining the sharp carination above and below, are more 

 inflated, and the aperture is wider and does not extend so far above 

 and below the body whorl as in the typical form, being in shape and 



