368 PROCEEDINGS OF THE ACADEMY OF [PaRT II 



inferior series of tubercles is never developed. It is also somewhat 

 larger than most Santo Domingan examples. 



S. p. pugiloides may be the ancestor of S. pugilis, or perhaps it is 

 not in the direct line. S. pugilis appears in its typical form in the 

 Pliocene of Florida and Costa Rica 



Strombi of the proximus-group are abundant shells in the Santo 

 Domingan beds. There are about 150 specimens in the Gabb col- 

 lection. 



As a whole, the series differs from S. pugilis and its varieties by 

 having the peripheral series of spines (or when spines are wanting, 

 the rounded shoulder) situated lower on the back of the last whorl, 

 the slope above it longer relative to that below it. This differen- 

 tial character is invariable. Also by the tendency to have an in- 

 ferior series of tubercles. These may be much reduced, or, in some 

 individuals wanting, yet there is never any trace of them in S. pugi- 

 lis. It appears to us that the evolutionary changes of the stock are 

 lost sight of if the forms amhiguus, bifrons, proximus and pugiloides 

 are submerged as synonyms of S. pugilis. Nothing with the char- 

 acters of the recent S. pugilis has been found in the Santo Domingan 

 or Bowden beds. 



Orthaulax inornatus Gabb. Plate XXX, figs. 13, 14. 15, 



Orthaidax inornatus Gabb, Proc. A. N. S. Phila. 1872, p. 273, pi. 9, fig. 3, 4, 

 (Feb. 11, 1873). Tr. Am. Philos. Soc, xv, p. 234. Guppy, Q. J. Geol. 

 Soc, 1876, p. 520, pi. 28, fig. 8. Dall, Bull. U. S. Nat. Mus. No. 90, p. 86, 

 pi. 11, fig. 4. Proc. U. S. N. Mus. LI, 1916, p. 509, pi. 88, fig. 9. 



Gabb selected a specimen of medium size for type (his fig. 3, 

 our PI. XXX, fig. 15). The callus envelopes the spire but does not 

 cover the apex. There is a low longitudinal callous swelling in 

 front of the posterior end of aperture and extending up the spire, 

 and a somewhat more distinct one opposite this on the left side, 

 becoming dorsal on the spire. The shell is thus somewhat com- 

 pressed dorso-ventrally. Anteriorly there are rather weak spirals. 



Length 55, diam. 27, dorso-ventral diam. 21.7 mm. 



The largest specimen (PI. XXX, fig. 14) is injured at the apex and 

 shows no calluses, the outline seen from above being regular, not it 

 flattened dorso-ventrally. 



Length 91.3, diam. 41.7 mm. 



In a young example (Gabb 's fig. 4, our PI. XXX, fig. 13) the su- 

 ture has begun to rise at the beginning of the tenth whorl. The 

 ninth has callous swellings on each side, and is therefore a little flat- 

 tened between face and back. The cavity is also somewhat narrow- 



