368 MAZATLAN UNIVALVES 
428. ALABA ALABASTRITES, 7. s. 
A. t. solidissima, alba, turrita; vertice anfr. uno et dimidie 
minimis, parum declivibus, immersis ; dein anfr. 11. tuberosis, 
levihus, marginibus divergentihus ; compactis, curtis, subplana- 
tis; dein anfr. normalibus subplanatis, parum compactis, liris 
solidis transversis circiter xvi. in lineas rectas & vertice basin 
versus continuis, suturis impressis ; liris ad peripheriam evani- 
dis; wmnbilico nullo; marginibus spire rectis, haud multum 
diwwergentibus, 
In this species, the sculpture of which is like a very strongly 
marked Chemnitzia, the tuberous whir.s 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°. 
Hab.—Mazatlan ; 1 sp. off Spondylus ; L’pool Col, 
Tablet 1726 contains the specimen. 
429. ALABA SCALATA, 7. S. 
A. t. tenuissimd, elongata, Chemnitzi-formi, alba ; vertice 
minimo, rotundato, parum declivi; dein anfr. 1. tuberosis, 
levibus, subrotundatis ; dein anfr. normalibus elongatis, lirulis 
transversis acutis (circiter xxv.) ornatd, circa basin subrotunda- 
tam vie continuis ; apertura subquadratd, ad basin angulaté. 
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. 
A430. PALABA CONICA, 2. S. 
2A. t. conicd, Trochoided, albidd ; anfr. primis subtuberosis, 
levibus ; dein valde divergentibus, anfr. normalibus iv. planatis, 
costis radiantibus circiter xvi., marginibus spire rectis convent- 
entibus, undulatis, ad peripheriam angulatam truncatis ; lirulis 
spiralibus supereuntibus, in spiré cireiter vi., in bast planatd 
circiter vi. rotundatis ; suturd excavata ; apertura subquadratd, 
ad basin angulatéd ; labio tenut, umbilicum parum monstrante. 
