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. &e. 
536. DUNKERIA PAUCILIRATA, 2. S. 
D. t. turritd, solidiore, alba ; vertice nucleoso haud producto, 
marginibus spire rectis haud superante ; anfr. rotundatis, 
postice subangulatis, suturis profundis, lirulis acutis circiter xiv. 
interstitiis latis, undatis, spiraliter tenuissiine striatis ; aper- 
turd elongata, subquadraté. 
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, lat. ‘027, div, 15°. 
Hab.— Mazatlan; 1 sp. off Chama; L’pool Col. 
Tablet 2007 contains the specimen. 
537. DUNKERIA SUBANGULATA, 7%. 8. 
D.t. subeylindricd, albé i vert. nucl. globoso, valde declivi, viz 
prominente, anfr. ., apice pene celato, marginibus spire sub- 
excurvatis haud superante ; anfr. normalibus v. convexis, infra 
suturam valde profundam vie angulatis ; lirulis transversis 
tenuibus circiter xx., ad suturam interdum continuis. ad basin 
evanidis, & striis spiralibus, parum elevatis, in anfr. penult. iv. 
eleganter cancellatis, interstitiis quadratis; stris circa basin 
rotundatam magis extantibus, tenuissime in lineis lirularum 
cancellatis ; aperturdé subovali. 
Variat, t. minore, liris exilioribus, erebrioribus. 
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 lirule, which 
cease at the suture, are continued round the base, in the form 
of minute lines decussating the spiral strie, 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, 
