1911.] NATURAL SCIENCES OF PHILADELPHIA. 353 



with alip-varixof the same type, but the dorsal hump is low and sharply 



plicate, as in S. cyphonotus. Some examples have several sharp, 



short folds below the suture in the space preceding the dorsal hump. 



The status of these Oligocene tricornute forms is not easy to decide. 



Our object now is merely to indicate the differential features of the 



several forms. 



MURIOID^B3. 

 Murex messorius Sow-. 



The Gatun form agrees well with recent specimens. The species 

 has been found also in the Santo Domingo Oligocene, but reported 

 by Gabb as M. recurvirostris (Geol. Santo Domingo, p. 201). 



Murex polynematicus n. sp. PI. XXVI, fig. 1. 



This form differs from the recent M . recurvirostris and the Oligocene 



much moie emphatic, high, less plicate. On either side of this hump the surface 

 is more flattened, being especially flattened and sunken in the last third, between 

 the dorsal eminence and the terminal varix. The varix is high and rather narrow, 

 preceded by a concavity, but no ripples. Other features as in S. cyphonotus, 

 except that the anterior canal is decidedly longer; lips white. 



"Length 26, diam. 10.4 mm. 

 " 29, " 12.2 " 

 " 23 " 10.2 " 



"This species was among the shells which Gabb had referred to Strombina 

 gradata. The longer canal, the narrow lip-varix and the high dorsal hump 

 readily distinguish it from S. cyphonotus" (Pilsbry and Johnson). 



" Strombina cyphonotus P. and J., n. sp. PI. XXV, figs. 6, 7. 



"Shell fusiform, solid, with rather slender, long spire, a little attenuated 

 above, elsewhere with straight, smooth outlines. The tip is broken in all speci- 

 mens seen, 7 + whorls remaining. These aie nearly flat, with the suture 

 impressed by reason of a narrow prominence of the upper edge of each whorl. 

 The penultimate whorl sometimes shows a few slight longitudinal wrinkles. 

 The last whorl is obtusely triangular in transverse section, having a low, oblique 

 hump on the left side of the ventral face, a dorsal hump near the suture sculptured 

 with several longitudinal ripples is preceded by a noticeable concavity, and a 

 massive varix behind the outei lip, rising from and merging gradually into the 

 general convexity of the back. A few ripples, distinct or faint, sculpture the 

 back of the varix. Anteriorly there are about 15 spiral grooves, the upper ones 

 coarse and deep, the lower fine and close. Elsewhere the surface is smooth. 

 The aperture is narrow, lips brown, the inner lip smooth, straight, elevated; the 

 callus within the outer lip bears about 9 small teeth. Anterior canal short and 

 slightly recurved. 



"Length 23.1, diam. 11 mm.; length of last whorl, from end of canal to 

 posterior end of the lip-varix 15 mm. 



"Other specimens of the type lot measure: 



"Length 21. S, diam. 10 mm. 

 " 23.1, " 10 " 

 " 21.5, " 11 " 



"Oligocene of Santo Domingo, W. M. Gabb. 



"This species was incorrectly identified by Gabb (Geology of Santo Domingo, 

 p. 221) with Columbella gradata Guppy, a conspicuously different Strombina of the 

 Bowden Oligocene. It is related to, and probably an ancestor of, the recent 

 West Coast Strombina dorsata (Sowerby), which differs by lacking ripples on the 

 humps, by its seamlike sutures, far weaker basal spirals, etc. 



