92 



solid structure, the peculiarities above noted in Anatina and Pandora, 

 the clavicle of the former, the folded margin of the latter, are united 

 in the following modified condition. The dorsal margin of the right 

 valve of Myadora becomes Consolidated into a tooth-like ledge or 

 projection, diverging from, on each side, the umbo, fitting into grooved 

 projections of similar construction in the left valve ; and by the di- 

 verging of these tooth-lilce projections a compact triangular cavity 

 is obtained for the insertion of the ligament, which in some species 

 is Avalled in, as it were, internally, not laterally as in Anatina, by a 

 moveable testaceous clavicle forming an angle with the diverging 

 ledges. 



The clavicles of Anatina and Myadora, it may be observed, are 

 very diiFerently situated with respect to the ligament, the one being 

 a side appendage, extending across the dorsal axis of the shell ; the 

 other an internal appendage, jDarallel as it were to the dorsal cixis. 



Of the following ten species, •vvhich I pro})ose to refer to this genus, 

 the grand type, Myadora slriata, is an inliabitant of Port Nicholson, 

 New Zealand, and the remainder are for the most part coUected by 

 Mr. Cuming in the Philippine Islands. 



1. Myadora crassa. Anatina crassa, Stutchbury, Zool. Journ. 

 vol. v. p. 100 ; Tab. Supp. xliii. f. 5 and 6. 



Conch. Iconica, Myadora, pi. 1. f. 1. 



Hab. ? 



This short rounded species is the only one at present known in 

 ■vvhich the right valve is concave. 



2. Myadora trigona, Myad. testd trigond, valde jįlano-depressd, 

 ■usque marginėm concenlrice striatd, striis prominentibus, quasi 

 carinulatis, prope marginėm anticam undatis ; umbonibus acuiis- 

 sime mucronato-elcvatis. 



Conch. Iconica, Myadora, pi. 1. f. 2. 

 Hab. Catanauan, province of Tayabas, island of Luzon. 

 Four odd valves only of this interesting little species were collected 

 by Mr. Cuming at the above-mentioned locality. 



3. Myadora planą. Myad. testd trigono-oblongu, aniicesubtrun- 

 catd, planissimd, concentrice striatd, striis subdistantibus, valvcc 

 sinistrce prominentioribus . 



Conch. Iconica, Myadora, pi. 1. f. 3. « and b. 



Hab. Baclayon, island of Bohol, Philippines (found in sandy mud 

 at the depth of seventeen fathoms) ; Cuming. 



This species is chiefly distinguished from its congeners, the Mya- 

 dora tincta and trigona, by its more oblong shape, 



4. Myadora ovata. Myad. testd ovatd, subtriangulari, valvd 

 sinistrd ventricoso-concavd, dextrd leviter convej;d, concentrice 

 striatd, striis eleuatis, prope margijiem anticam subobsolelis, valvcc 

 dextrce numerosis, confertis, sinistrce prominentibus , subdistantibus, 

 umbonibus depresso-incurvis. 



Conch. Iconica, Myadora, pi. 1. f. 4. 



