256 TESTACEOUS MOLLUSCA, 
like scales; dorsal edge straight, anterior rather sloping, ventral 
somewhat rounded; anterior angles rounded: vertex somewhat 
hooked. 6...8. Panama. 
P. Zetanica. Gray in Yates N. Zealand.—Gray Dief. Zeal. 
Triangular, elongated, blackish, convex, with rather close radiating 
ribs armed with close short semicylindrical hollow spines, within 
purplish, pearly. New Zealand. Differs from Squamosa in beng 
smaller, black, and having the anterior base more truncated. New 
Zealand. 
P. Lanceotata. Sow. Z. P. 1835. Lanceolate, towards the dor- 
sal edge with radiating longitudinal riblets, almost unarmed towards 
the posterior ventral margin, riblets distant, muricated, with dis- 
tant rather long subrecurved scales; dorsal edge straight, anterior 
rather straight and somewhat sloping, ventral subventricose. 3} 
..73. Puerto Portrero. 
P. Invrrata. . Chem. 8. p. 215. f. 771.—W. t. 12. f. 5.—D: p. 
Very tumid, uniform olivaccous horn-coloured, moderately elonga- 
ted, triangular satchel-shaped, with radiating unarmed ribs which 
do not extend to the anterior base or the wide posterior ventral area 
which is covered by subreticulated wrinkles and defined by an ob- 
solete longitudinal keel: hinge margin somewhat shorter than the 
posterior ventral, the former nearly straight and armed at its edge 
with small prickles, the latter incurved near the beaks and convex 
as it approaches the anterior base, which is arcuated and subangu- 
lated at each extremity. 6. Nicobar Isles. 
P. Rucosa. Sow. Z. P. 1835. Large, rough, triangular, with 
obtuse radiating ribs, anteriorly broad and rounded ; ribs anteriorly 
armed with large elongated irregular somewhat recurved foliaceous 
tubular scales: dorsal edge straight; posterior ventral somewhat 
contracted. 6..9. Panama. } 

TRIBE MALLEACEA. 
Foliaccous, more or less inequivalve ; having the ligament marginal, 
somewhat linear, and either simple or interrupted by the crenulations. 
CRENATULA. 
Subequivalve, flattened, somewhat distorted and lamellar ; no special 
opening for the byssus; hinge lateral, linear, margined and crenated ; 
the crenulations in a regular series, callous,and somewhat hollowed, 
receiving the ligament. 

' See too the P. Vireata, and Dertopes, of Menke’s Specimen 
N. Hollandize Molluscorum. 
