228 



ON THE TOPOGKAPHY AND GEOLOGY 



I. f IX s i f o r m i s . Gabb, n. s. 



Shell miiuitc, .shovt-fnsiforni, spire twice as long as the mouth, ayIioiIs seven, flattened on the sides, apical angle 

 ■wide, suture obsolete, surface polished ; body whorl sub-angulated below, slightly convex and produced in advance. 

 Aperture sub-angulated, lips simple, columella slightly twisted, anterior end produced so as to form a small but well 

 marked lip-like canal. Length .08 inch, width .04 inch. 



ARCHITECTONICA. Bolt. ■ . • ^ 



A. q u a d r i s e r i a t a . Sby., sp. . . 



Boliirium, id. 8by., Quart. -Tour., Vol. YI , p. 81, pi. 10, fig. 8. • . . , ' 



Id. Guppy, Quart. .Jour., Vol. XXIL, p. 29L 



Common. ■ 



" ■ TORINIA. Gray. ' " . 



T. rotundata. Gabb, n. s. 



Shell moderate in size, spire elevated, apical angle rounded; as also the outer mai-giii; base of body whorl convex ; 

 outer margin marked by two large libs with a smaller one between ; upper surface with four ribs, under surface with 

 five or six, of which one forms the umbilical margin and is strongly crenate ; umbilicus broad, inner face of the whorl 

 marked with two large and three linear alternating ribs ; the whole surface crossed by strong lines of growth 

 breaking the revolving ribs and producing a cancellated appearance. Aperture nearly circular. Diameter .5 inch, 

 height .35 inch. 



Rare. In the sciilptm-e of the nppcr snrface, this is not very nnUke the preceding- 

 species, hut its rounder form sufhciently distinguish them. 



CONUS. Linn. 



It is with decided rehictance that I have taken up tlie enumeration and separation 

 of the Cones of Santo Dominiro. I am safe in asserting- that I have never undertaken a 

 more diflicult ta,sk,-and while I have ahmost suffered under an embarrassment of riches 

 in the great numbers of specimens I have had to study, that same profusion is 

 rather the source of the difficulty than a means of relief. With a few shells, a fictitious 

 division can easily be made ; but in series of hundreds, nay thousands, where opportunity 

 exists for the study of all the varieties, this labor is not so easy. I have based the 

 following arraiigement on the careful and prolonged examination of over 2,300 good 

 specimens, and believe that, in the main, I am more correct than my predecessors 

 could have had the means of being. Since I have been obliged in most cases to work 

 in this difficult genus without the advantage of the color patterns, and therefore to 

 depend almost entirely on form, my results cannot have that certainty which accom- 

 panies the study of recent shells. Still I have had this assistance in pai't, and have 

 availed myself of it. By comparison of the larger suites at my disposal, I have 

 learned that the a]>ical angle, within certain limits is, of itself of little value; the 

 presence or absence of spiral striai on the tops of the whorls is not always a safe 

 character, but the most varial)le one of all is in the surface strise or grooves on the 

 sides, more especially at the anterior end of the shell. In recent specimens, where 

 the colors are so marked, this latter character is but little noted ; but in the fossils it 



