Bird 
122 
7. PLACUNANOMIA ALOPE. 
Upper valve flat, smooth, radiately striated. Scars two, well sepa- 
rated, rounded, equal-sized. 
Hab. California; Lady Katherine Wigram. 
Two upper valves in British Museum. 
++ European. 
8. PLACUNANOMIA PATELLIFORMIS. 
Shell suborbicular, convex or quite flat, radiately striated ; inner 
disk greenish. Apex rather within the dorsal margin. 
The upper muscular scar of the dorsal valve very large, oblong ; 
the lower one small, roundish, on the lower part of the hinder margin 
of the upper one. 
The peduncle of the cartilage with a triangular cavity in front, 
under the tip, and continued in an oblong rib-like ridge towards the 
centre of the shell. 
Anomia patelliformis, Linn. S. N. 1152; Nov. Act. Upsal. 1773, 
i. 42. t. 5. f. 6, 7; Retzius, Nov. Gen. Test. ii. ; Sars, fide Mus. Cu- 
ming ; Loven, Moll. Scand. 30; Forbes § Hanley, Brit. Moll. 334. 
t.56; Wood, Index Test. t. 10. f. 10, not Chemn. 
Squama Magna, Chemn. Conch. vii. 87. t. 77. f. 697. 
Anomia Squama, Gmelin, S. N.; Schumacher, Essav. 
Ostreum striatum, Da Costa, Brit. Conch. 162. t. 11. f. 4. 
Anomia undulatim striata, &c., Chemn. Conch. viii. 8. t. 77. f. 699. 
Anomia undulata, Gmelin, Syst. Nat. i. 3346; Mont. Test. Brit. 
157. t. 4. f. 6; Maton §& Racket, Trans. Linn. Soc. viii. 103 ; Turton, 
Conch. Dict. 4. Bivalves, 230. t. 18. f. 8,9; Dillw. R. S. 1. 289; 
Wood, Index Test. t. 11. f. 9. 
Ostrea striata, Pulteney in Hist. Dorset, 36 ; Donovan, B. Shells, 
ii. t. 45; Mont. T. B. 153, 580. 
Anomia striata, Loven, Index Moll. Scand. 29 ; Forbes §& Hanley, 
Brit. Moll. 336. t. 55. f. 1, 6. t. 53. f. 6. 
Hab. Coast of Europe. British Seas, Lister. North Sea, Sars, fide 
Mus. Cuming, n. 51. 
This species is easily known from the other European species by 
being generally thicker and regularly radiately ribbed, and greenish ; 
but the number and position of the muscular scars at once separate it 
from all the multiform varieties of that species. Some authors, over- 
looking the latter character, have been inclined to regard it as a mere 
variety. 
I may remark, that the large series of this species which I have 
examined has shown that the position of the two muscles is liable to 
a slight variation ; in by far the larger number of specimens the small 
lower muscle is quite close to and confluent with the scar of the upper 
larger muscle, but in a few specimens it is separated from the upper 
larger one by a small interval or space. This has induced me to be- 
lieve that probably the three West Indian species of the genus may 
prove, when a larger series of specimens have been collected and com- 
pared, only varieties of the same species. 
