156 Bulletin 39 338 



A single specimen from the Gatun of Codes Creek. It agrees 

 almost exactly with Dr. Maury's type specimen of Natica 

 Youngi iroYo. the Miocene of Santo Domingo in size and form, 

 but differs in its smaller umbilicus and smaller umbilical callus. 

 The Costa Rican shell has the aspect of a Neverita, 



Gatu7i Stage; Codes Creek, near Old Harbor, C. R. 



Section STIGMAULAX Moerch 

 Piatica Guppyana Toula Plate 13, figures 13, 14, 15 



Natica {Stigmaulax') Guppyana Toula, 1909, Jahrb. der K-K Geol. 



Reichsanstalt, Wien, vol. 58, p. 696, pi. 25, fig. 6. 

 Natica Guppyana Brown and Pilsbry, 191 1, Proc. Acad. Nat. Sci, 



Phila., vol. 63, p. 360. 



This species stands intermediate in its sculpture and form 

 to the N. canrena Linnaeus and N. sulcata Born, both recent and 

 fossil Miocene species. In Guppyana, the sculpture consists of 

 even, wide and deep sulcations, which cross the face of the whorl 

 from the upper suture to the umbilicus. They are in fact the 

 continuation of the tangential sutural plicae of N. canrena. With 

 further growth these sulcations may become obsolete on the mid- 

 dle of the whorls until they are lacking from the greater part of 

 the shell except in the immediate vicinity of the upper sutures 

 and on the umbilical angle. This change in sculpture is not seen 

 to the same extent on all shells and some specimens may remain 

 strongly grooved and sulcated even when large and mature. In 

 other cases (in general with shells from the Banana River) 

 only very young shells have the sulcation continuous across 

 the face of the whorl, but soon become smooth, leaving the plica- 

 tions only about the upper suture and on the umbilical angle. 

 Such shells resemble closely .'V. canrena, but in addition to 

 the grooving of the umbilical angle, have a larger and more 

 exanded aperture. 



The A^. sulcata Born still remains to be found in Costa Rica 

 and Panana. It is abundant as a Miocene fossil in Santo 



