368 MAZATLAN UNIVALVES 



438. ALABA ALABASTBITES, n. s. 



A. t. solidissimd, alba, turrit d ; vertice anfr. uno et dimidio 

 vtiinimis, parum declivibus, immersis ; dein anfr. iii. tuberagi*, 

 Icevibus, marginibus divergentious ; compactis, curtis, subplana- 

 tis ; dein anfr. normalibus subplanatis, parum compactis, liris 

 solidis transversis circiter xvi. in lineas rectas a vertice basin 

 versus continuis, suturis impressis ; liris ad peripheriam evani- 

 dis ; umbilico nullo ; marginibus spires rectis, Jiaud multum 

 diver gentibus. 



In this species, the sculpture of which is like a very strongly 

 marked Chemnitzia, the tuberous whirls are compact, thimble- 

 shaped, and rather diverging, so that the last of these has a 

 rather larger diameter than the first of the normal ones ; which 

 then proceed at a rather less angle of divergence. The only 

 specimen is broken below ; it has three normal whirls, and 

 measures long. '055, long. spir. '035, lat. '027, div. 27. 

 Hob. Mazatlan ; 1 sp. off Spondylus ; L'pool CoL 



Tablet 1726 contains the specimen. 



429, ALABA SCALATA, n. s. 



A. t. tenuissimd, elongatd, Chemnitzi-formi, alba ; vertice 

 minima, rotundato, parum declivi ; dein anfr. iii. tuberosis, 

 Icevibus, subrotundatis ; dein anfr. normalibus elongatis, lirulis 

 transversis acutis (circiter xxv.) ornata, circa basin subrotunda- 

 tam vix continuis ; aperturd subquadratd, ad basin angulatd. 



This Chemnitzoid shell is not unlike Parthenia scalariformis ; 

 but presents the tuberous whirls with the rounded top instead 

 of the sinistral apex. It has only one normal whirl and a half, 

 and measures long. '036, long. spir. '02, lat. '018, div. 20. 

 Hab. Mazatlan ; 1 sp. off Spondylus ; L'pool Col. 



Tablet 1727 contains the specimen. 



430. ? ALABA CONICA, n. s. 



?A.t. conicd, Trochoidea, albidd ; anfrJ primis subtuberosis, 

 IcBVibus ; dein valde diver gentibus, anfr. normalibus iv. planatis, 

 costis radiantibus circiter xvi., marginibus spirce rectis conveni- 

 entibus, undulatis, ad peripheriam angulatam truncatis ; lirulis 

 spiralibus supereuntibus, in spird circiter vi., in basi planatd 

 circiter vi. rotundatis ; suturd excavatd ; aperturd subquadratd, 

 ad basin angulatd ; labio tenui, umbilicum parum monstrante. 



