THE NAUTILUS. 135 



pressed and irregularly, deeply lacerated above. The aperture is 

 slightly longer than wide : peristome narrowly reflexed, thin, 

 fluted, and having a small lobe at the upper extremity. 



The operculum shows three whorls and a gray sunken nucleus 

 externally, the whorls flat and tangentially striate, separated by 

 a deep narrow 7 suture. The inner face is concave and light 

 yellow. The edge shows the two layers separated by a very 

 deep cleft. 



Length 15, diam. of last whorl, above the aperture 7 mm. ; 

 longest axis of aperture outside peristome 6 mm. 



Locality. Ojo de Agua range, between Guantanamo and 

 Ramon de las Yaguas. Types No. 111445 A. N. S. P., para- 

 types in Ramsden collection. 



This species differs conspicuously from D. architectonicum in 

 both shell and operculum, but the latter has the very deep peri- 

 pheral cleft characteristic of the genus. It was a great surprise 

 to come upon a new species of this group. 

 RHYTIDOPOMA TOLLINI, n. sp. PI. vi, fig. 5. 



The shell is umbilicate, conic, composed of 4^ strongly con- 

 vex whorls. The summit is somewhat mamillar and distorted, 

 the first whorl extremely convex, smoothish, next half whorl 

 narrower. The last two whorls have a sculpture of very irreg- 

 ular, in part twinned axial lamina? which are enlarged at inter- 

 vals in spiral bands, of which there are about 12 on the last 

 whorl at the aperture; those on the inner (umbilical) side 

 crowded, the rest widely spaced and larger, giving the appear- 

 ance of coarse, low, spiral cords. The suture is irregular by 

 the unequal prominence of the lamina?. The last whorl is 

 barely free at the aperture. Peristome is simple, not expanded, 

 but having a small lobe at the sutural extremity. 



The operculum lodges lid-like upon the edge of the peris- 

 tome. It is circular, concave within, flat externally, composed 

 of about 7 narrow, closely-wound whorls, which are obliquely 

 striate and parted by a rather deep, narrow suture. 



Length 7, diam. 7 mm. 



Locality. Fifteen miles south of Media Luna, on the Pilon 

 road, collected by 0. Tollin. Type no. 111444 A. N. S. P., 

 paratypes in coll. Ramsden. 



