144. MAZATLAN BIVALVES 
Genus PECTUNCULUS, ZLam.* 
196. Pec#uncuLvus 1NzZQUALIS, Sow. 
Proce. Zool. Soc. 1832, pt. . p. 196: [non Gray in Beech. Voy. 
pe l52,, pl. 42, £3: (y.. Ave. in: P. ZS. 1843, p. 79) nec 
Krauss, Sudafr. Moll. p.18.| — Hanl. Descr. Cat. p. 166.— 
Rve. Conch: Ic. pl. 4, f. 16. " 
=P. Pectiniformis, Wood Suppl. pl. 2, f.11, non Lam. (teste 
Hanl.) 
?=P. assimilis, Sow. Proc. Zool. Soc. 1832, pt. i. p. 196.— Mull. 
Syn. Test. Viv. p. 189.—Rve. Conch. Ic. pl. 4, f. 15.—B. M. 
Cat. D’ Orb. Moll. p. 80. no. 712.—C. B. Ad. Pan. Shells, 
p. 256, no. 411.— Hanl. Descr. Cat. p. 167, note. . 
Only two specimens having been found adult of this ex- 
tremely beautiful shell, no opportunity existed for ascertaining 
its power of variation; but C. B. Ad. thus remarks of P. 
assimilis, ““In respect of colouring (no two being alike) the 
species does not appear to be well distinguished from P. 
inequalis: nor is the distinction in sculpture much more con- 
stant.” Surface of the shell with a variable, small number of 
ribs, covered, as well as the interstices, with fine ribs decussa- 
ted in the ‘‘strung fig” pattern. Margin most beautifully 
crenated by each; interior surface covered with fine lines ; 
anterior part short, ligament subtruncated. A very young 
valve, ‘04 across, displays 3 teeth on each side, with the larger 
ribs only developed outside and decussated : ligament in a pit 
asin Limopsis. Long. 1°33, lat. 1°31, alé. °9. 
Hab.—Bay of Panama and Real Llejos ; in sandy mud, 10 fm. ; 
Cuming.—Mazatlan ; extremely rare; L’pool Col,—(P. as- 
similis) Puerto Portrero, Bay of Guayaquil; in sandy mud 
and gravel 8-12 fm.; Cuming.—EHcuador, Guayaquil, D’ Orb- 
igny.—Panama ; under stones, in calcareous gravel, between 
one-quarter tide and low water mark, rare; C. B. Adams.— 
Mazatlan, Lieut. Green. 
Tablet 664 contains the smallest valve.— 665, the finest 
specimen. E 
197. PectuncuLUs P MuLTIcostatus, Sow. 
Proc. Zool. Soc. 1832, pt. ii. p. 195 —Rve. Conch. Ic. pl. 5, 
f. 26.—Hanl. Descr. Cat. p. 165, pl. 19, f. 36—B. MW. Cat. 
D Orb. Moll. p. 80, no. 711. 
* ¢¢The first name for these shells is Axinea, Poli. If Pectunculus, Lam. (not . 
Adanson) is to be used, it should be limited to the ribbed species.” A. Addams, ms. 
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