MAZATLAN UNIVALVES 417 



SECTION A. Species Odostomoidece. 

 503. CHBYSALLIDA OVATA, n. s. 



Chr. t. baud parvd, solidd, ovatd, albd ; verticc nucleoso 

 parvo, omnino celato ; marginibus spires parum excurvalis ; 

 anfr., paucioribus quoad magnitudinem, iv. et dimidio, subro- 

 tundatis ; suturd impressd ; liris tuberculosis transversis, testd 

 juniore subdistantibus, testd adultd contiguis, marginibus spires 

 vix parallelis ; lirulis spiralibus, in spird iv. vix monstranlibus, 

 circa peripheriam et basin rotundatas vi. validis, rotundatis, 

 interstitiis parvis rugoso-decussatis ; aperturd parum contractd, 

 peritremati continuo, labio interdum rimulam umbilicalem 

 monstrante ; plied solidd, obtusd, parum celatd. 



This species and the next are at the confines of the group, 

 with which they agree in general habit, sculpture, and con- 

 tinuous peritreme, while the form is that of the typical Odos- 

 tomise. The pattern closely resembles that of Chr. nodosa, 

 and the apex that of Chr. fasciata, from both of which it differs 

 in its broad expanding form, the adolescent shells being like 

 the adults. The lip is not thin, but agrees with the group in 

 being much more solid within, as is shewn by the broken 

 shells, of which there were several, though very few of any age 

 were perfect. The largest (a monster for the group) measures 

 long. '155, long. spir. *08, lat. '083, div. 35. 

 Sab. Mazatlan ; very rare, off Spondylus ; I/pool Col. 



Tablet 1968 contains the youngest, the oldest, and an inter- 

 mediate specimen. 



501 CHRYSALLIDA NODOSA, n. s. 



Chr. t. subconicd, solidd, alba ; vertice nucleoso minimo, 

 prominente, marginibus spirce vix ex cur vatis parum super ante ; 

 anfr. normalibus v. latis, subplanatis ; lirulis spiralibus iv. 

 transversis usque ad xvii. sili parallelis, ad inter sectiones nodosis; 

 tuberculis rotundatis, validis, transversim attingentibus, spirali- 

 ter plerumque separatis ; lirulis transversis supra suturam 

 impressam declivibus ; lirulis spiralibus in basi rotundatd 

 vi. rotundatis, interstitiis tenue decussatis ; plied columellari 

 parum celatd, validd, obtusd ; aperturd (in t, adultd) oblong A, 

 parum contractd, ad basin product d, peritremati continuo, labio 

 haud tenui. 



