8o STUDIES IN GEOLOGY, No. 3 



von da gegen die Naht verschmalert. Sie tragen 8 Spiral- 

 rippen, von denen die dritte von unten, die auctf den Kiel 

 bildet, am starksten ist. Die anderen verlaufen gleichmassig 

 in gleichen Zwischenraumen. Zwischen den 3 unteren sind 

 noch feine lineare Spirastreifchen wahrnehmbar. Lange 95 

 mm., Breite bei der Miindung 23 mm." Grzybowski, 1899. 



In some specimens there is a fine subsidiary thread in the 

 first three interspaces above the carina. Ordinarily, how- 

 ever, these spaces are free of secondary sculpture. Those 

 forms which show the interstitial threads have but four 

 heavy threads above the carina instead of the normal five. 

 Apical angle moderate. Growth-lines similar to those of 

 T. nelsoni var. trullissatia are visible but not prominent. 



Length (fragment of 6y 2 whorls) 82 mm.; maximum 

 diameter, 26.5 mm. ; estimated length of complete speci- 

 men, 105 mm. 



This species is somewhat similar to T*. mimetes Brown and 

 Pilsbry, 71 from Gatun, though not close; it differs in form 

 much as it does from T. nelsoni var. trullissatia (q.v.), with 

 additional variance in sculpture. T. subgrundifera Dall, 72 

 from the Chipola beds of Florida, is closer than any other 

 American form. It differs in being more delicate, with the 

 keel finer and more attenuate, and in having more definite 

 subsidiary threads. T. subangulqta var. spirata Brocchi (2), 

 from the Helvetien and later of Europe, is more closely 

 related than either of the other two forms mentioned. It 

 differs chiefly in its more refined, more delicately chiselled 

 appearance. 



Upper Zorritos. Quebrada de las Alturas. 



Turritella infracarinata var. zomtensis n. var. 



PLATE III Fig. n. 

 Shell large, solid ; whorls convex, rounded, about twelve to 



"Idem. 



"Trans. Wag. Inst, vol. 3, pt.. 2, p. 313, pi. 22, fig 23, 1892. 



