117 



i882. PlicaUila Jiorrida Dunker, Ind. Moll. Mar. Japon., p. 247, pi. XI, fig. 6, 7. 

 1895. Plicatula Jiorrida Pilsbry, Cat. Mar. Shells Japan, p. 143. 

 igo6. Plicatula Jiorrida Owston, Japan. Loochooan Shells, p. 35. 



Plicahtla Jiorrida is closely allied to P . chinensis and may turn out to be only a local 

 variation of it. The shells, which I refer to this species agrée with Dunker's descriptions and 

 figures, and are distinguished from those of P. chinensis by the ridges on the surface being 

 fewer, more angulate and much more spinous. 



Distribution : — P. Jiorrida has so far been recorded from the Japanese seas only. 



In the "Siboga" collection it is represented by a young shell from the Anchorage East 

 of Sailus Besar, Paternoster Islands (St. 3 1 3), and an odd greatly weathered valve dredged 

 from St. 98 (6°9'N., i20°2i'E., 350 mètres). 



4. Plicatula muricata Sowerby. 



1873. Plicatula muricata Sowerby in Reeve, Conch. Icon. XIX, Plicatula, pi. III, figs. 9, a,b. 



1874. Plicatula muricata Thielens, Descr. Coll. Paulucci, p. 61. 



1882. Plicatula muricata Dunker, Ind. Moll. Mar. Japon., p. 247, pi. XI, fig. 4. 



1890. Plicatula muricata Paetel, Cat. Conch. Samm., III, p. 241. 



1895. Plicatula muricata Pilsbry & Stearns, Cat. Mar. Moll. Japan p. 143. 



1906. Plicatula muricata Owston, Japan. Loochooan Shells, p. 35. 



1911. Plicatula muricata Pelseneer, "Siboga" Lamellibranches (Anat.), p. 32, pi. XII, fig. 12. 



This species was, so far as I can find from the literature, never described by Adams, and 

 Sowerby apparently was the first to publish figures and description of it in "Conchologia Iconica". 



The young shells of P. mttricata are trigonal and not so oblique as the older shells of 

 this species. The young shells are very closely and regularly pleated, but in older shells the 

 sculpture becomes somewhat irregular and the fine spines appear as raised, elongated spines of 

 the type found on shells of P. australis or even P . Jiorrida. Concentric growth lines are also 

 very well marked in young shells. 



Distribution : — P . muricata was described from spécimens of unknown habitat in the 

 British Muséum collection. Dunker referred shells from Japan to this species and other authors 

 hâve since recorded Japanese spécimens under this name. 



In the "Siboga" collection there is a good séries of shells from the Western Entrance 

 Samau Strait (St. 59), St. 98 (6°9^N., i20°2i'E., 350 mètres), between the Islands ofWowoni 

 and Buton, northern entrance of Buton Strait (St. 204) and near Kei Islands (St. 260). 



5. Plicatula sp. 



Two shells dredged from St. 164 (i°42'.5S., i30°47'.5 E., 32 mètres) are greatly worn 

 spécimens of this genus attached to bits of shells of Ostrea and Arca respectively. They do 

 not correspond to any previously described species, but in view of the large number of species 

 that hâve- been described already, I do not propose describing a new species based on such 

 unsatisfactory material. 



