FEIEND OR FOE 99 



which in 1876 he named Pachygrapsus advena; one was a 

 i\ aufdlograjjsus (or Planes) minutus^ a species scarcely ever 

 found in the Mediterranean ; the remainder belonofed to 

 two species, which M. Catta speaks of as Plagusia squa- 

 mosa and Plagusia tomentosa. The latter, a South African 

 species, should rather, it seems, be designated Plagusia 

 chabrus (Linn.), and the former Plagusia depressa (Fa- 

 bricius). It was this last-mentioned one that was the most 

 numerous, being present in hundreds. As an Atlantic 

 species, it might not have had far to come. The point 

 of special interest, however, lies, as Catta explains, in 

 showing the effects on distribution that may be produced 

 by unconscious human agency. 



Family 4 . — Pinnotheridoi. 



The carapace is usually more or less membranaceous, 

 convex or depressed, with the antero-lateral margins entire 

 or very slightly dentate. The ' front,' orbits, and eye- 

 stalks are very small. The buccal frame is usually arcuate 

 anteriorly. The third maxillipeds have the fourth joint 

 well developed, and usually the third also, the fifth articu- 

 lated at the apex, or at the front inner angle, or more 

 rarely the front outer angle, of the fourth. The chelipeds 

 in the adult male are small or moderately developed. The 

 walking legs are slender and generally naked, with the 

 seventh joint stiliform, unarmed. The pleon of the male 

 in general does not cover the whole width of the sternum 

 between the last pair of legs. 



The crabs of this family are small, and many of them 

 live in the shells of bivalve molluscs, tests of Echini, tubes 

 of annelids, and other borrowed habitations. Miers dis- 

 tributes five-and-twenty genera over four sub-families. 



Pinnotheres, Latreille (in Bosc), 1802, was known to 

 the ancients under the same name, but more commonly 

 under the name Pinnoteres. It is a great pity that 

 Latreille did not adopt the latter, which is in all pro- 

 bability the older form. Small as the difference in sound, 

 the difference in sense is considerable. Pinnotheres means 



