184 Remarks on the Geiuis Aiilacodiscus Ehrb. [Sess. 



surface of the ocean waters as well as in their most profound 

 depths, may be induced to prosecute their observations still 

 more assiduously in this ample domain, to co-operate in the 

 earnest if humble attempts of the many home and foreign 

 workers now endeavouring to elucidate the story of their life, 

 their minute structure when alive or after death, the still un- 

 known mechanism of their movements, and the riddles of the 

 endo-parasites to whose ravages they, in common with the 

 highest of living organisms, are at all times exposed. 



The genus Aulacodiscus embraces some of the most elegant 

 forms among the Diatomacea^. Marine in its habitat, its species 

 are in part met with in fossil deposits only, but they are also 

 occasionally found in the vicinity of land — continental or insular 

 — in tropical or temperate waters. Among deposits its repre- 

 sentatives are to be found in that of Mors, Jutland ; of Sim- 

 birsk and Sysran, Eussia ; of Barbadoes ; of Monterey, Santa 

 Monica, Santa Marta, and Santa Maria, California ; of Szent 

 Peter, Szakal, and Kekko, Hungary ; of Eichmond and Peters- 

 burg, Virginia ; of Calvert County, Nottingham, and Piscataway, 

 Maryland ; of Augarten ; and of Oamaru, New Zealand. From 

 oceanic deposits specimens have been procured in the Pacific 

 by the Challenger, and in the Indian Ocean by the Gazelle. 

 Guanos from Bolivia, Peru, Ichaboe, San Filipe, Patos Island, 

 Patagonia, and South Africa, may also be examined with 

 success. The shores of Great Britain and of the European 

 continent have yielded but a small harvest hitherto, but many 

 recent elegant valves have been procured from New Zealand, 

 New Caledonia, Sumatra, Java, Samoa, Celebes, Japan, the 

 Sandwich and Philippine Islands, Ceylon, Labuan, the Nicobal? 

 Islands, King George's Sound, California, Peru, San Francisco, 

 Sierra Leone, the river Congo in W. Africa, Teneriffe, and other 

 localities. It thus appears that whilst deposits afford the most 

 accessible hunting-ground, ballast of ships trading with foreign 

 ports may frequently be examined with a good hope of dis- 

 covering some of the clioicest gems in this department of 

 research. 



I must refer the members to the monograph which I have 

 recently had the privilege of submitting to the Eoyal Micro- 

 scopical Society of London for a systematic description of the 



