AKT. 15 NEW MARINE MOLLUSKS FEOM PANAMA — BARTSCH 9 



are marked by strong axial ribs, which are most strongly developed 

 at the periphery and which diminish in strength both anteriorly and 

 posteriorly. Of these ribs 11 are present on all the turns. The first 

 and second postnuclear whorls are marked by three spiral cords, 

 which are almost equal in strength, on the third and fourth turns 

 the anterior of these three cords becomes much emphasized and the 

 posterior one enfeebled. On the last whorl a fourth cord is appar- 

 ent. The three at the periphery form strong humps. In addition 

 to these strong spiral cords, the entire surface of spire and base is 

 marked by finer spiral threads, of which eight are present between 

 the summit and the second spiral cord; three are present on the 

 second spiral cord, and two in the space between the second and 

 third; there is one strong thread on the third spiral cord and three 

 fine threads between the third and fourth; the fourth also has a 

 strong spiral thread on its summit. The base is short, moderately 

 well rounded and marked by a continuation of the axial ribs and 

 three strong spiral cords almost as strong as the anterior one of the 

 spire. The space betw^een the supraperipheral and infraperipheral 

 cord is crossed by five spiral threads, while the space between the 

 first and second basal cord is also crossed by five spiral threads; 

 the space between the second and third basal cords is marked by 

 three spiral threads. The columella is short and thick and is marked 

 on the posterior half by three strong spiral cords a little less in 

 strength than those on the base, but in continuation of that series. 

 Three spiral threads are present between the stronger cords on the 

 posterior half of the columella. The anterior half of the columella 

 is marked by eight closely approximated slender spiral cords. The 

 incremental lines and the spiral threads on spire and base render 

 the general surface slightly reticulated. Aperture of irregular 

 outline, strongly channeled anteriorly, feebly so posteriorly. Outer 

 lip slender at the edge, reenforced within immediately behind the 

 edge, bearing a strong oblique fold near the posterior angle and a 

 little anterior to this two approximated denticles, which are partly 

 fused. Anterior to these there are two smaller denticles, and a heavy 

 denticle marks the posterior termination of the canal at the anterior 

 portion of the aperture. The inner lip is reflected over the columella 

 as a thick callus, which also extends over the parietal wall. This 

 callus bears two slender threads near the posterior angle, followed 

 by an elongate thread much heavier than these two, which faces 

 the heavy thread at the posterior angle on the outer lip and con- 

 stricts this part of the aperture almost into a canal ; anterior to this 

 fold are five slender oblique threads equaling the posterior two in 

 strength, while on the columellar wall eight slender, rounded 

 denticles are present. 



