MARYLAND GEOLOQICAI, SURVEY 193 



nally, and somewhat also internally, and marked by several tooth-like 

 lines on the inner side. Inner lip also distinct and somewhat thick- 

 ened with several tooth-like striae, the posterior end of the aper- 

 ture being slightly channeled and the front strongly so; beak dis- 

 tinctly constricted at its junction with the body whorl. Surface 

 granularly cancellated with nearly direct vertical lines or ridges 

 and raised spiral lines, forming granules or asperities at their inter- 

 section, and the last whorl having a single lip-like varix. Spiral lines 

 eight or nine in number on the boly whorl, and the vertical lines eighteen 

 or twenty, exclusive of the lip and varix. Volutions above the last not 

 possessing lip-like varices.'' Whitfield, 1894. 



Whitfield described the variety elongata as follows: 



"A number of specimens of full growth, having many of the features 

 of T. trivittatoides above described, occur in the collection. They vary 

 from one-fourth of an inch to five-sixteenths of an inch in length, and 

 are proportionally much more slender than are those of that species. 

 They also possess a greater number of vertical lines, and two additional 

 spiral lines on the body whorl. The surface features are much like 

 those of that species, but on many of them the spiral lines are more 

 distinctly raised ribs, and the line of nodes below the suture more dis- 

 tinctly separated from and proportionally larger than those below. The 

 thickened outer lip is the same as on that shell, as also is the lip-like 

 varix within the limit of the body whorl, but the teeth-like ridges on 

 the columella and on the inside of the outer lip appear on most speci- 

 mens somewhat stronger in proportion to the size of the shell, while 

 the proportional length of the spire, as compared to that of the body 

 whorl, is considerably greater. These features are so marked as to 

 render it unsafe to include these specimens under the same specific head 

 with T. trivittatoides" Whitfield, 1894. 



It is impossible to decide definitely here of the value of the var. elon- 

 gata for the New Jersey fossils. The differences upon which it was 

 established appear to be slight and the Maryland specimens which appar- 

 ently represent both forms cannot be divided. 



Length (restored), 14 mm.; diameter, 6 mm. 



Occurrence. — Choptank Formation. Jones Wharf. Calvert For- 

 mation. Plum Point, 3 miles west of Centerville. 

 13 



