Zoological Society. 281 



3. A Monograph of the genus Monoptygma of Lea. 

 • By Arthur Adams, R.N., F.L.S. etc. 



Genus Monoptygma, J. Lea. (? Menestho, Miill.) 



Animal unknown. 



Shell subulately turreted, transrersely striated, apex simple, acute ; 

 aperture oval, longer than wide, rounded and entire in front ; colu- 

 mella with a single oblique fold. 



This genus differs from Actaon in being elongated, and in having 

 an oblique fold, instead of a transverse plait on the columella. 



1 . Monoptygma striata. Gray. M. testa turrito-suhulatd, so- 

 lidd, oUvaced, anfractibus planis, transversim sulcatis, sulcis 

 prqfundis, distantibus ; aperturd oblongd, intus albd. 



This species, which is typical, is a very thick and strong shell, with 

 a somewhat convex lateral outline, and strongly transversely grooved 

 across the flattened whorls. Mus. Cuming. 



2. Monoptygma fulva, A. Adams. M. testd turrito-subulatd, 

 graciliori, solidd, fklvd, anfractibus planis, transversim sulcatis, 

 sulcis prqfundis, distantibus; aperturd oblongd, intus fused. 



This elegantly-formed shell is more slender than M. striata, and 

 of a different colour ; the transverse grooves are also much closer 

 together, and their edges are rounded ; the twist of the columella is 

 not so distinct, and the aperture is brown internally. Mus. Cuming. 



3. Monoptygma granulata, A. Adams. M. testd ovato-tur- 

 ritd, albd, solidd, anfractibus planiusculis, gradatis, longitudi- 

 naliter corrugato-plicatis, transversim sulcatis, sulcis profundis, 

 valde distantibus ; interstitiis Icevibus ; aperturd oblongd, colu' 

 melld plied subproductd. 



This is a rather short and obtuse white and solid species, very 

 strongly grooved transversely, and with the whorls longitudinally 

 corrugately plicated. Mus. Cuming. 



4. Monoptygma lauta, A. Adams. M. testd turrito-subulatd, 

 albidd, tenui, subpellucidd, anfractibus planiusculis, longitudi- 

 naliter eleganter striatis, transversim sulcatis, sulcis distanti- 

 bus, interstitiis crenulatis ; aperturd oblongd, columelld obliqud 

 et curvatd. 



A very beautifnlly-sculptured species, dredged from 10 fathoms, 

 at Bolinao, by Mr. Cuming ; the outline is subulated, and the whorls 

 rather flattened and longitudinally striated. Mus. Cuming. 



5. Monoptygma amcena, A. Adams. M. testd ovato-acuminatd, 

 tenui, subpellucidd, albidd, longitudinaliter substriatd, anfrac- 

 tibus convexiusculis, transversim sulcatis, sulcis valde distanti- 

 bus, interstitiis eleganter punctatis ; aperturd oblongd, antice 

 dilatatd, columelld rectd. 



This is a most exquisite species, both in form and sculpture ; the 

 whorls are rounded and pimctate-striate, and the shell is nearly pel- 

 lucid; it is from Bolinao, 10 fathoms water. Mus. Cuming. 



