NARRATIVE OF THE CRUISE. 
859 
301 mm.), and the deep-sea species Ascorhynchus cjlaber, Hoek, Palleno'psis mollissima, 
(Hoek), and Nymphon hamatum, Hoek, are also remarkable for their dimensions, especially 
when they are compared with species of the same genera inhabiting shallow water. 
“ It has not been possible to demonstrate by the aid of the deep-sea material any 
relationship of the Pycnogonida either with the Arachnida or with the Crustacea. It is 
necessary, therefore, to consider them, provisionally at least, as a distinct group (Class) 
Fig. 323 . — Colossendeis proboscides, (Sabine). 540 fathoms. Natural size. 
of Arthropoclous animals. Their body consists of a cephalon, a thorax, and a rudi- 
mentary abdomen. The cephalon is united with the first segment of the thorax, and 
three free thoracic segments follow behind this coalesced segment. When comparing 
different genera of Pycnogonida a great diversity is shown with regard to the number 
of cephalic appendages ; sometimes there are three pairs of them, sometimes only two, 
sometimes one, and occasionally they are all wanting. This last circumstance, however, 
