366 mazatljlN univalves 



Alaba, (described in English by Messrs. Adams as a subgenus 

 of Ceritliiopsis,) there did not appear cause for adding another 

 name for those species which do not accord with their diagnosis. 

 The description of Tubcria is however retained, in order to 

 include the whole group. Their true position, of course, can 

 only be satisfactorily shewn when the animals have been 

 examined. 



425. Alaba stiPEALiEATA, n. s. 



A. t. tenv\ conica, albidd, posteafusco irregulariter strigatd ; 

 nitidd, subdiaphand , marginibva spirce variantihus ; vertice 

 ndnimo, rotundato, parum decHvo ; dein avfr. iv. tiiberosis, 

 marginihus ijhts mimisve parallelis, suturis parvis, tenuissiTne 

 transversim Ihidatis, lird spirali supramediand ; dein anfr. 

 iv. siihnormalibus, Icevibus, suhplanatis, conicis, suturis Jiaud 

 impressu ; periplierid vix rotundatd, aperturd suhquadratd, 

 ad basin suhangulatd ; dein anfr. iii. normalibus, tumidis, 

 spiraliter ienue striatis, striis di stantibus ; varicosis, varicibus 

 qiwque in anfractu tribus, attingentibus, tumidis, concavis ; 

 aperturd subovali ; labro tenui, ad basin undato ; labio tenuis- 

 simo, parvo ; columella vix intortd. 



About 50 specimens were found of this remarkable shell ; 

 but most of them so very imperfect, and so different in char- 

 acter at different periods of growth, that only the late and 

 fortnmate discovery of a fresh adult specimen, led to their 

 identification. In its usual adolescent state, it might rank as 

 a Eulimclla, but for the want of the Chemnitzoid apex. It 

 has one whirl, sufficientlj' sloping to give the top of the striated 

 portion a mammillated appearance. The first four whii'ls look 

 like a thimble, and differ from the rest not only in sculpture, 

 but in the margins which are nearly parallel ; while afterwards 

 they are more or less divergent, resembling in their irregularity 

 some species of Stylifer. After however making four whirls 

 in an apparently normal condition, it changes again, and as- 

 sumes a Bittioiil aspect. The flattened whirls become tumid, 

 their smooth surface spirally striated, the porcellanous white a 

 rusty brown in irregular stripes, and the periphery rendered 

 irregular l)y tumid hollow varices, three in a whirL The 

 mouth which has always been angiUar at the base of the 

 columella, now develops a very slight wave, scarcely amounting 

 to a notch. As far as the specimens shew, this is the end of its 

 changes. It most closely resembles a W. Indian species, 

 Cingula tervaricosa, C B. Ad., which however is larger, with 



