COOKE : ON THE GENUS CLAUSILIA. 263 



but have been placed by von Mollendorff, tibetajia in subg, 

 Formosana, serrata and gihhosula in subg. Hemi'phcediisa. They 

 represent, witli one exception, the furthest known western outposts 

 north of the HiniaLiyas of the great Phcedusa group. 



Japan. — The Clausilia of Japan, while very closely related to those 

 of China, exhibit in many respects an independent and characteristic 

 development. The whole group has been worked out byH. A. Pilsbry 

 with a thoroughness and originality which are quite beyond praise, 

 and his writings form practically the sole material for a study of the 

 genus as it exists in these islands. 



Southern Japan and Formosa are separated from the mainland of 

 Asia by a shallow sea, which in no place exceeds a depth of 200 m. 

 The Loo Choo Islands, which link Japan with Formosa, are separated 

 both from Japan and from Formosa by much deeper water, the 

 archipelago to the south of Kiu Siu (Tanegashima and the Linschoten 

 Islands) being practically part of that island, and separated by deep 

 water from tlie Loo Choos proper. In the result we find that while 

 the Clausilia of Japan and Formosa are closely related to those of 

 China, those of the Loo Choos are markedly different, not only from 

 China, but from Formosa and Japan. To quote from Pilsbry (46) : 

 " LuchupJKednsa has been found nowhere else but on this group [one 

 species on islands off Kiu Siu]. Zaptyx extends into the southernmost 

 provinces of Kiu Siu, and, probably borne by the Kuro Shiwo, has 

 reached Hachijo, an islet 100 miles off Izu province. Stereophcedusa 

 and Hemiplmdusa range further, being common throughout Japan . . . 

 but the species of the Loo Choo Islands belong to a special group of 

 Jffemiphcediisa which has not been found elsewhere. The sections 

 Fuphmlusa and Megalophcedusa, so characteristic of Japan, are wanting 

 in the Loo Choos. As regards species, not one is common to the Loo 

 Choos and any other land. No characteristic Formosan forms of 

 Clausilia have been found in the Loo Choo group." "As a whole the 

 Claiisili(B of this group are more specialised than those of China or 

 Japan, and bear out the proposition that insular faunas ape more 

 rapidly than those of larger or continental areas " (Pilsbry 46). 



The southern and central portions of Japan proper (Kiu Siu and its 

 outliers, Shikoku, Southern and Central Hondo) are rich in Claxisilia, 

 some species of the sub-genus Megalophcedusa being the largest and 

 handsomest in the world. In Northern Hondo and Yesso the numbers 

 appear to fall off rapidly, though probably exploration is not complete. 

 Excluding synonyms and varieties, the total number so far recorded 

 for the whole group is about 155, of which 107 occur in Japan proper, 

 33 in the Loo Choos, and 15 in Formosa. 



Japan proper. Loo Choos. Formosa. 

 Hcmiphcsdiisa group ... 77 12 9 



Zaptyx group .... 9 20 4 



Eiiphadusa group . . ' . 21 1 2 



107 33 15^ 



^ Including Euph. aculus, Bens., which also occurs in Japan. 



