434 MAZATLAN UNIVALVES 



of the latter. It agrees with all the other sections of the 

 family in having its limits badly defined. When the forms 

 from various seas are better known, the entire family will 

 need revision ; meanwhile, for convenience' sake, these species 

 are separated with a name in remembrance of Prof. W. Dunker, 

 the learned author of Ind. Moll. Guin., Monogr. Mytil. &c. 



536. DUNKEBIA PAUCILIBATA, n. S. 



D. t. turritd, solidiore, alba ; vertice nucleoso Jiaud producto, 

 marginibus spira rectis Jiaud super ante ; anfr. rotundatis, 

 postice subangulatis, suturis profundis, lirulis acutis circiter xiv. 

 interstitiis latis, undatis, spiraliter tenuissime striatis ; aper- 

 turd elongatd, subquadratd. 



This species somewhat resembles Parthenia scalariformis, 

 but is entirely destitute of the columellar plait. The last 

 whirl has perished : the remaining six measure long. '083, 

 long. spir. *055, lot. '027, div. 15. 

 Hob. Mazatlan ; 1 sp. off Chama ; JJ'pool Col. 



Tablet 2007 contains the specimen. 



537. DUNKEEIA SUBANGCJLATA, n. S. 



D. t. subcT/lmdricdj alba ; vert. nucl. globoso, valde declivi, vix } 

 prominente, anfr. ii., apice pcene celato, marginibus spirce sub- 

 excurvatis haud super ante ; anfr. normalibus v. convexis, infra 

 suturam valde profundam vix angulatis ; lirulis transversis 

 tenuibus circiter xx., ad suturam interdum continuis. ad basin 

 evanidis, a striis spiralibus, parum elevatis, in anfr. penult, iv. 

 eleganter cancellatis, interstitiis quadratis; striis circa basin 

 rotundatam magis extantibus, tenuissime in lineis lirularum 

 cancellatis ; aperturd subovali. 



Variat, t. minore, liris exilioribus, crebrioribus. 



The outline of this elegantly cancellated species, when 

 young, resembles D. paucilirata : it is then however much 

 broader and more angulated, with more numerous ribs, and a 

 scarcely twisted columella. In the adult state the lirulse, which 

 cease at the suture, are continued round the base, in the form 

 of minute lines decussating the spiral striae , as these decussate 

 the ribs above. A very young sp. with two normal whirls 

 measures '032 by '023. The largest in the L'pool Col. with 

 four normal whirls, measures long. '067, long. spir. '045, 



