8 



THE VOYAGE OF H.M.S. CHALLENGER. 



The number of times at which Pycnogonida were dredged at certain depths is shown 

 in the following table : — 



It thus becomes apparent that what Davidson has shown for the Brachiopoda, 

 holds also in the case of the Pycnogonida, that they are very seldom found in depths 

 exceeding 500 fathoms ; out of about 100 dredgings in depths of from 1 to 500 fathoms, 

 Pycnogonids were brought up twenty-six times, while in depths varying from 501 to 

 3000, they were obtained only thirteen times out of 300 dredgings. 



The following statement shows the range in depth at which the genera of Pycnogonida 

 hitherto known have been found. The total number is twenty-seven genera, of which 

 eleven are true Httoral forms. Of the sixteen remaining genera there are five 

 of which I am quite uncertain as to the depth at which they are found, and 

 four for which the depth does not exceed 50 fathoms. Then there are two {Pallene 

 and Pycnogonum), which, as a rule, inhabit depths not exceeding 120 fathoms, but 

 which in a single case were found at depths almost reaching 500 fathoms (Pallene 

 malleolata, G. 0. Sars, at a depth varpng between 191 and 459 fathoms, and P«/c?;o- 

 yonum litorale, dredged hj Smith and Harger, at a depth of 430 fathoms). Hence 

 there remain only five genera of Pycnogonida, species of which may truly be called 

 deep-sea inhabitants; they are the gcnern Nymphon, Ascorhyncliiis, Oorhynchits, Colos- 

 sendeis, and Phoxichilidmm. 



