319 ' Costa Rico Miocene — Olsson 147 



cal sculpturata reveals no distinction betv/een them. Both are 

 variable in their coiling from closely wound, narrow cylinders to 

 more open, umbilicate coils. The sculpture is much the same. 



In the United States, this fossil is limited to the Upper 

 Chesapeake Miocene. In the Antillean and South American re- 

 gions, it is found in the Bowden beds of Jamaica, the Gurabo 

 formation of Santo Domingo, the Quebradillas limestone of Por- 

 to Rico, the Springdale beds of Trinidad, from the Gatun beds 

 near Cartagena, Colombia and Mexico. 

 Gatun Stage: Gatun Stage, C. Z. 



Water Cay, Pa7ta??ia. 



Coll. ^, 5, East Qrape Point Creek. 



Comadre Creek. 



Genus S!LSQUAR!A I^amarck 

 Siliquaria modesta Dall, var. (smosiensis, n. var, Plate 12, figure 4, 5, 6 



cf Siliquaria modesta Dall, Mus. Comp. Zool. , vol. 9, p. 39. 



cf Siliquaria modesta Dall, 1889, Bull. Mus. Comp. Zool., vol. 18, p. 

 260, pi. 26, fig 4. 



This shell is very abundant in certain marl}^ and sandy beds 

 in the coralline limestones of the Limon Peninsula and elsewhere. 

 Specimens in perfect condition are very difficult to obtain, the shell 

 being ver}^ fragile and delicate. There are no longitudinal threads 

 and the shell is smooth, except for the grovs^th lines which are 

 sometimes a little irregular. 



We have associated this shell with the 6^. ??todesta of Dall, a 

 recent species and recorded by Dr. Dall from several stations in 

 the West Indies and the Gulf of Mexico, in waters ranging from 

 94 to 805 fathoms in depth. The fossils differ in being more 

 loosely coiled and at the later stages long drawn out. 



Dr. Maury's 5. guarabensis from the Miocene of Santo Do- 

 mingo is more irregular in its habitus of growth and the surface 

 of the shell carries faint longitudinal threads. Gabb has des- 



