368 MAZATLAN XTNIVALVES 



4S8. Alaba alabastbites, n. s. 



A. t. soUdissimA, alhd, tnrrita ; vertice anfr. uno et dimidit 

 minimis, parum declivibiis, immersis ; dein avfr. iii. tuherosis, 

 IcBvihus, margiiiihns divergentlhus ; compactis, curtis, suhplana- 

 iis ; dein anfr. normalihiis aubplanatis, parum compactis, lirit 

 tolidis traiisversis circiter xvi. in, lineas rectos a vertice basin 

 versus cotitinuis, sutiiris impressis ; liris ad, periplieriam evani- 

 dis ; umbilico nullo ; marginibiis spine rectis, haud multum 

 divergentibus. 



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

 marked Chemnitzia, the tuberous whir.s are compact, thimble- 

 shaped, and rather diverginor, 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, die. 27". 



Mab. — Mazatlan ; 1 sp. off Spondylus ; L'pool Col, 



Tablet 1726 contains the specimen. 



4SQ. Alaba scalata, n. s. 



A. t. ienuissimd, elongatd, Chemnifzi-formi, alba ; vertice 

 minima, rotundato, partem declivi ; dein anfr. iii. tiiberosis, 

 Icevibus, siihrotundatis ; dein anfr. normalibus elongatis, lirulis 

 transversis acutis (circiter sxx.) ornatd, 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°. 



Sal). — Mazatlan ; 1 sp. off" Spondylus ; L'pool Col. 



Tablet 1727 contains the specimen. 



430. ? Alaba conica, n. s. 



?A. t. eonicd, Trochoided, albidd ; anfr! pri mis subtuberosis, 

 Icevibus ; dein valde divergentibus, anfr. normalibus iv.planatis, 

 costis radiantibus circiter xvi., marginibus spirce rectis conveni- 

 entihus, undulatis, ad periplieriam angulatam truncatis ; lirulis 

 spiralibits supereunfibus, in spird circiter vi., in basi planatd 

 circiter y\. rotitndatis ; sutiird cvcavatd ; aperturd subquadratd, 

 ad basin angulatd ; lahio tenui, umbilicum parum monstrante. 



