MAZATLAN UNIVALVES 423 
511. CHRYSALLIDA FASCIATA, 2. 8. 
Chr. t. parva, ovoided, alba ; vertice nucleoso parvo, declivi, 
omnino celato ; marginibus spire excurvatis ; anfr. normalibus 
iv.—v., clathris circiter xvii. twherculosis, lirulis ii. plus 
minusve conspicuis, decussantibus, cingulo quoque super suturam 
extante, interstitis utrinque tenue decussatis, ornatd ; basi 
rotundata lirulis circiter iv. spiralibus subacutis cinctd, inter- 
stitiis latis, lineis clathra continuantibus tenue decussatis ; plicd 
columellart celata, parva, obtusa; peritremati vix continuo, 
labio tenut. 
This species has some characters in e¢mmon with Chr. mar- 
ginata, C. B. Ad. (Pan. Shells, no. 226) from which the number 
of ribs at once distinguishes it. In many respects it resembles 
Chr. ovulum, from which it differs in its breadth and larger size, 
in the prominence of the suprasutural band, the fineness of the 
few basal striz, and the sunken position of the nuclear whirls 
on the broadly truncated (‘01 across) spire. Some of the 
specimens are short and broad in proportion, which is the 
character of the earlier stage generally. A young shell, with 
two anda half normal turns, measures long. ‘036, long. spir. 
O17, lat. 027, div. 30°. The largest, unusually elongate, yet 
not quite mature, long. 083, long. spir. 046, lat. °042, div. 23°. 
Hab.—Mazatlan ; 20 sp. off Spondylus ; Z’pool Col. 
Tablet 1981 contains 5 specimens ; two very young, one 
dwarf, one mature, broad, and one almost mature, elongated. 
512. CHRYSALLIDA OVULUM, 7. s. 
Chr. t. minima, gibbosd, alba, solidiore; vertice nucleoso 
“Chr. communt” simulante, marginibus spire valde excurvatis, 
haud superante; anfr. normalibus 11. et dimidio, interdum 
clathrulis transversis circiter xvii., interdum lirulis spiralibus 
iv. nodulosis superantibus ; lacund suturali profundd, in basin 
rotundatam, effusam, haud continua ; apertura compacta, labro 
parum tenurt, intus solido; plicé columellari obtuso; Urulis 
rotundatis in basin spiralibus ciretter vi., interstitiis minimis, 
ovix decussatis. . 
About 70 specimens of this stumpy little species were found, 
differing from the dwarf forms of Chr. communis in the strength 
of the spiral riblets, which generally break the transverse 
bars into coarse tubercles, and in the small number and promi- 
nence of the rounded basal strie. The whirls are very few, 
