16 SPIRAXIS. 



2. S. MIRABILIS (C. B. Adams). PI. 1, fig. 3. 



"Shell rather long and conic, with two-thirds of each whorl 

 enormously inflated, gradually more abruptly with the pro- 

 gress of growth, so as to give to the shell the form of a screw ; 

 subtranspareiit, whitish ; with numerous microscopic spiral 

 striae, and very distant transverse erect lamellar ribs, which 

 have smooth rounded edges, and are most elevated at the sum- 

 mit of the convexity of the whorls, and diminish much over 

 the anterior extremity of the shell; spire with rather convex 

 outlines; apex with the inflation proportionally much longer 

 and the ribs slightly elevated ; whorls about seven, with an in- 

 distinct suture ; aperture modified by the form of the last 

 whorl at its termination, and by the remarkably prominent 

 and much twisted columella, nearly into the form of the 

 figure 8. Length .1 inch; breadth .062 inch." (Adams'). 



Jamaica : 



B'uliiims inira'biUs C. B. AD., Contrib. to Conch, no. 2, p. 

 29 (Oct. 1849) .REEVE, Conch. Icon, v, pi. 84, f. 622 (Dec. 

 1849). Spiraj-is inirabilis AD., Contrib. no. 9, p. 168. PFR., 

 Monogr. iii, p. 472. 



Adams' description is given above. The first whorl is 

 smooth or nearly so, and strongly elevated. The second and 

 third whorls have delicate longitudinal riblets or lamina? at 

 rather wide intervals. Then the adult sculpture of strong, 

 compressed, triangularly projecting ribs sets in. These ribs 

 are strongest on the greatly swollen upper half of each whorl; 

 and when broken are seen to be hollow. The surface between 

 is finely stria te spirally ; color grayish corneous. Length 3.6, 

 diam. 1.5 mm. 



The internal structure is like S. inusitatus except that the 

 parietal lamella is not so strong in the specimens opened, and 

 there is no minor axial lamella, below the large one. 



There is no material variation in the series I have seen in 

 the Adams and Academy collections. 



Section Euspiraxis Pfeiffer. 



PFR., Malak. Bl. ii, 1855, p. 167; no diagnosis, no type 

 selected. MARTENS, Die Hel. 1860, p. 34, type S. costulosa Ad. 



