igog.] N. AnnandaIvE : The Indian Cirripedia Ped'unculata. 103 



shallow-water crabs, from the Gulf of Suez to Java, perhaps to Japan; D. cor, also 

 common, from the East Coast of Africa to Java and Sumatra; D. angulata from the 

 Persian Gulf to Java ; D. tridens from the Bay of Bengal to the Philippines. The only 

 Indian species as yet reported from the Atlantic is a deep-sea form, namely, D. gery- 

 onophila ; but the shallow-water species D. sinuata is closely allied to D. lowei from 

 Madeira and D. mülleri from the Atlantic Coast of North America, if it is not actually 

 identical with them, while D. rhinoceros is probably the Oriental representative of the 

 North American D. forrestii. D. hathynomi and D. stella have as yet only been found 

 in Indian seas, the latter on one occasion, the former in several rather widely separated 

 localities ; the host of D. hathynomi, Bathynomus giganteus, also occurs in the Carib- 

 bean Sea, but there is no evidence that the barnacle accompanies it in its American 

 habitat. 



As regards the vertical range of the species of this genus it is clear that they 

 may be divided roughly into two sections, one only occurring at considerable depths 

 (about 100 fathoms and over), the other onty in shallow water and on the surface; 

 but there are several exceptions to this rule; nor does it appear to be possible in 

 most instances to make a distinction between pelagic and littoral forms. Few species 

 have been taken at a greater depth than 200 fathoms. In Indian seas D. hathynomi 

 ranges from 180 to about 500 fathoms, while D. geryonophila (which has been taken at 

 still greater depths in the Atlantic) has been obtained by the '' Investigator' ' from a 

 depth of between 200 and 300 fathoms in the neighbourhood of the I^accadive Islands. 

 Probably these two forms do not occur at a depth of much less than 200 fathoms. 

 D. tridens and D. sinuata, however, extend from the littoral zone to a depth 

 approaching or greater than 100 fathoms; D. stella was taken at one of 180 fathoms 

 and D. rÄwocßf OS between 60 and 100 fathoms. The remaining species appear to be 

 confined to shallow water and to the surface. 



In his recent account of the Pedunculate Cirripedes of the ' ' Siboga ' ' Expedition 

 Hoek notes that the only deep-sea species (D. welleri) taken by that expedition is the 

 largest species of the genus known, having a capitulum about 12 mm. in greatest 

 length. I have, however, examined several specimens of D. warwickii with a capi- 

 tulum about 10 mm. long and one with it over 11 mm. long, while the smallest species 

 of the genus with which I am acquainted are D. stella and D. rhinoceros, both 

 from considerable depths. There can be no doubt, therefore, that the deep-sea 

 species are not always larger than those from shallow water ; but there is undoubtedly 

 some connection between the size both of individuals and of species and their habitat ; 

 those species found within the confined space of the gill-chamber of a decapod are, for 

 instance, always small. Even in the case of external species, however, it is rare for 

 individuals to attain their full dimensions, probably because their host gets rid of 

 them periodically by casting its skin ; the great majority of the specimens of D. war- 

 wickii I have examined have been less than 5 mm. long. 



The influence which the species of Dichelaspis exert on their hosts, if they 

 exert any influence at all, is a point worth considering but still in need of investi- 

 gation. Unfortunately the only species of the genus I have seen alive are D. 



