38 FOSSILS FBOM SOUTHEEN UNITED STATES— BALL. vol. xvm. 



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TEREBRA (ACUS) BIPARTITA, Sowerby. 



Terebra MparUta, Sowerby, Quart. Joiirn. Geol. Soc. Londou, YI, pt. 1, p. M, 

 1849. Not= T. Upartita, Deshayes, 1859. 



Habitat. — Old Miocene of Santo Domingo, at Ponton, and in the Cliip- 

 ola beds (2213), Calhoun County, Florida. Specimens in the Acad- 

 emy of Natural Sciences and the U. S. National Museum (Nos. 113G53, 

 113910). 



Variety hipartlta., s. s. — Shell acute, with the sutural sulcus prominent 

 and set off by a deep sulcus, which cuts ribs and all, from the rest of 

 the whorl, where the spiral threading is remarkably clear-cut, uniform, 

 and elegant, not overriding the narrow, sharp-edged ribs. Santo Do- 

 mingo and Chipola. Longitude, 23; maximum diameter, 5..5 mm. 



The pillar of this form seems to be simple and smooth in all the 

 sijecimens I have seen. 



Variety sjnri/era, Dall. — Shell with the ribs feeble, the spiral sculp- 

 ture more prominent than the ribs, especially two rather narrow spirals 

 just in front of the sutural band, and overriding the ribs with close- 

 set, even, distinct, coarse, rounded threads, which fail on the canal; 

 pillar distinctly grooved or biplicate. Loiigitude, 30; maximum diam- 

 eter, 8 mm. Ponton, Santo Domingo. 



This form is larger, and the shell increases in diameter more rapidlj'' 

 than in the type. It may prove to be worthy of specific rank with 

 more material, in which case the varietal may be used as a specific 

 name. No. 113051, U. S. N. M. 



It recalls, in its relation to the tyi)e, the relation of T. indenta, Con- 

 rad, to T. (lislocata, Say. 



Variety oligoniitra, Dall. — Shell slender, with 12 or more whorls, 

 crossed by numerous very sharp, thin, sigmoid ribs, with wider inter- 

 spaces, over which lie (between the sutures four and on the base four 

 smaller) strap-like, flat spirals, with much wider interspaces, failing on 

 the i)illar; the whole surface is also finely spirally striate; the pillar 

 long, twisted, biplicate; the suture very distinct. Longitude. 38; max- 

 imum diameter, 8.5 mm. River Amina, Santo Domingo. 



This form is more slender, the spirals are sparse and strap-like, 

 instead of crowded and rounded; the fine spiral striation is not seen on 

 the previously mentioned forms. No. 11375G, U. S. N. M. 



Variety cirruSj Dall. — Shell much smaller and j)roportionally more 

 slender; spirals flat, strap-like, irregular, with narroM^er interspaces, 

 overrunning very low and imrrow sharp ribs with wider interspaces; 

 whorls, 12 or more, flatfish; pillar sharply biplicate. Longitude, 25; 

 max imum diameter, 5.5 mm. Eiver Amina, Santo Domingo. No. 113752, 

 U. S. N. M. 



This l)ears to the variety oligomitra much such a relation as T.jyrotexta, 

 Conrad, does to the more delicate types of T. (lislocata, Say. It mayj 

 prove to be worthy of specific rank. 



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