CRUSTACEANS 



sometimes greenish, sometimes brightly mottled with reds and browns, with 

 the advantage of not being disguised by shaggy hairs. Small as it is, the 

 diversified denticulation of its carapace gives it a look of distinction. The 

 other crabs of the quartette in question are species of Portunus. The 

 members of this genus have habits and functions which are hinted at in 

 the trivial names, swimming crabs, fiddlers and cleansers. When an in- 

 solent fellow proposed to appoint Epaminondas to be chief scavenger, the 

 great Theban general promised that even in such an office he would take 

 care to serve the state efficiently. Great and small among Crustacea grandly 

 render us this service in aquatic realms, and the Portuni are called cleansers 

 only because they are a little more conspicuous than the rest in doing this 

 work. Most crabs are able to swim, but the Portuni and some others 

 have an advantageous modification of structure for this purpose. The 

 hindmost legs, instead of an awl-like ending, have the last two joints 

 flattened out, to form, as it were, fins or oar-blades, by help of which 

 rapid motion through the water is accomplished. Also these joints in 

 action, being geniculated or bent one towards the other, produce some 

 resemblance to the motions of a fiddler's elbow. In this genus, and like- 

 wise in Pirimela, it will be noticed that the pleon or infolded tail part of 

 of the male has only five segments distinct, whereas all the seven are 

 distinct in the female. 



Portunus pusillus (Leach) occurs all round England, chiefly in 

 moderately deep water. Metzger reports it from twelve and fifteen 

 fathoms on the Norfolk coast.' The title of dwarf fin crab, or dwarf 

 swimming crab, well suits an animal of which, according to Bell, the 

 ordinary length is one-third of an inch, though the measurements of its 

 carapace may occasionally swell to four-fifths of an inch in length by a 

 full inch in breadth.* The carapace is rugose and irregularly granulated, 

 having the regions well marked, the lateral dents not very acute, and the 

 three-lobed front well advanced, with the middle lobe projected beyond 

 the other two. 



Portunus holsatus (Fabricius), reported by Metzger from twenty-three 

 fathoms depth on this coast,' besides being considerably larger than the 

 largest Portunus pusillus, has a much smoother carapace, with sharper 

 lateral teeth, the front not advanced, and its middle tooth not projecting 

 teyond the others. Attention may here be called to the circumstance 

 that all the crabs that have been mentioned have the normal five more or 

 less acute lateral teeth or ' dents,' with the exception of Cancer pagurus, in 

 which the dents become broad shallow lobes, nine in number. 



In the tribe of the Oxyrrhyncha, or sharp-beaked crabs, two species 

 were taken by the German expedition on the coast of this county, both 

 at the same station and in the same depth as the Pilumnus and Pirimela 

 previously noted. One of these is Hyas araneus (Linn.). This, by its 

 specific name, attempts to monopolize the title of spider-crab, which is 

 often applied to all the members of its tribe. Adam White calls it the 



* Nordseefahrt der Pommerania, p. 295. * Bell's British Stalk-eyed Crustacea, p. 114. 



* Nordseefahrt der Pommerania, p. 294. 



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