92 



TUB GEOLOGIST. 



banded by five or six striae, and the upright portion by four or five. In the body-whorl 

 the space posterior to the angle is subcorneal, for a second angle, which in the smaller 

 whorls is the limit of the upright part, and also the line of suture, is here reduced to a 

 rib. Posterior to this keel are about eight spiral striae. 



In form this closely resembles P. marginata (D'Orb.) and P. 

 Fittoni (Forbes). 



Pleurotomaria Jukesii (d. sp.). 



Few-whorled, subcorneal, moderately depressed, half as high as wide, consisting of five 

 elevated whorls, which regularly increase in size. The whorls are nearly four times as wide 

 as high, and each twice the diameter of that which preceded it. The filled-in sinus is ele- 

 vated like a string and situate on the upper part of the whorl, which it divides into an 

 upper and a lower region. The upper is very convex, deeply impressed at the suture, 

 horizontal, and rather narrower than the lower region, which is flat and oblique, being 

 inclined at an angle of about 60°. The slit of the sinus is equal in length to the dia- 

 meter of the shell. The whole of the upper side is marked with very fine and close 

 spiral ribs. 



Under side not seen. 



Most nearly related to P. perspectiva in form of whorl, but well 

 distinguished by its few whorls. 



Trochus. 



Shell conical, three-fourths as high as wide ; composed of about four whorls, which 

 are flat, one-fourth as high as wide, and have the sutures deeply impressed. Each whorl 

 is ornamented with four spiral striae, of which each supports a row of sharp, elevated tuber- 

 cles. The tubercles are separated by spaces about as wide as those which divide the 

 rows. The tubercles of the anterior row r s are successively placed one between two tubercles 

 of the row above, so that other oblique rows are formed parallel to the labial side of the 

 shell. The base is flat and spirally striate. 



Trochtjs. 



Conical, a little higher than wide, not umbilicated ; commonly composed of four or five 

 whorls, which are slightly convex. Each whorl is about two and a half times as wide 

 as high and encircled by about six spiral striae, which are elevated like cords ; the inter- 

 spaces are much wider than the ribs ; they are flat. The highest rib is larger than the 

 others, and in most cases less projecting ; it and all the other costae are crossed by very nu- 

 merous, oblique, narrow indentations, giving to each rib the look of a twisted rope. The 

 side passes under to the base in a large curve. The base is marked by a greater number 

 of striae than the side ; they are less elevated, rather closer together, and not bead-like. 

 Shell rather thick. The suture is wide and deeply impressed. 



Very nearly related to T. Geinitzii (Rss.). 



(?) Ftrsus. 



Subangularly fusiform; composed of four or five whorls. Spire nearly half the length 

 of the shell. Whorls angular, rapidly enlarging, twice as wide as high. Ornamented 

 with four sharp, narrow, rather elevated ribs, below which, towards the columella, are a 

 number of tine striae, rather distant apart. The whorls are so coiled that two (? one) of 

 the four costae are covered by the body-whorl. The most prominent rib is the most 

 posterior, which projects like a cord. The space between it and the suture is flat and in- 

 clined at a small angle, and the space below it, for half the body-whorl, is parallel to the 

 axis. The slope of the ledge of the upper part of the whorl appears to become greater 

 as the shell increases in size. Mouth pear-shaped. The shell is finely striated spirally, 

 there being some twelve lines betweeu two ribs, and these striae are crossed by still finer 



