3^5 



Costa Rica Miocenb — Olsson 



153 



whorl is enlarged, forming a cord-like expansion about the upper 

 suture; sutures indistinct and appressed; sculpture of fine, ir- 

 regular and somewhat wavy spiral lines and indistinctly alter- 

 nating in strength; growth lines as typical for Hausiator (not 

 visible on the base of our specimen), commence at the lower 

 suture and pass straight and parallel to the longitudinal axis 

 of the shell to the middle of the whorl where the\^ become 

 bent 'and continue obliquely to the left or towards the aper- 

 ture to the upper suture. 



Length (2^ whorls), 49, diameter 23 mm. 



A very rare species and represented in our collection by 

 only two imperfect specimens. It appears to be closely related 

 to the T. cartagensis Pilsbry and Brown from the Gatim of 

 Colombia. The full-grown Costa Rican shell was probably 

 longer and more attenuated and each whorl is prominently 

 elevated or ridged just in front of the lower suture. 



Gatun Stage: Rio Banana beyond Hill No. 5. 



Genus ALABA A. Adams 



Alaba turrita Guppy, 1896, Proc. U. S. Nat Mus., vol. 19, p. 321, pi. 

 28, fig. 7. 



Guppy 's figure of his type specimen from Jamaica agrees 

 very closely with our specimen from the Estrella River. The 

 whorls are finely spiralled with low ridges which are obsolete 

 from the upper parts of the whorls. Bach whorl carries 2 or 

 more broad, smooth varices formed during resting stages. 

 The last whorl is strongly angulated by these varices. 

 Height 5, diameter 2.25 mm. 



Gatun Stage: Coll. 7, Estrella River. 



