NARRATIVE OF THE CRUISE. 
859 
301 mm.), and the deep-sea species Ascorhynchus glaber, Hoek, Pallenopsis 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 proboscidea, (Sabine). 540 fathoms. Natural size. 
of Arthropodous animals. Their body consists of a ceplialon, 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, 
