PINNOTHERES. 
PINNOTHERES. Latreille , Bose, 
CANCER. Linn ., Gmel ., Penn. 
ALPHvEUS, Daldorff. 
Antenna externa setace®, brevissim®, (articulis tribus primis majoribus,) in oculorum cantho 
interno insert®. 
Pedipalporum geminormn externorum caulis internus uni-articulatus ad apicem subabrupte 
acuminato-rotundatus, palpigerus. 
J cduin par anticum ®quale; paria 2, 3, A et 5 simplicia, (maris pr®sertim) compressa, pari 
quinto breviore: Ungues arcuate acuti, validi. 
Abdomen in utroque sexu 7-articulatum. 
Lest a ovato-orbiculata, orbiculato-subquadrata aut transverse subquadrata. 
Oculi crassi pedunculo brevi, in fronte inserti inter se dissiti. 
External antenna: setaceous, very short, inserted at the internal corner of the eye, the three 
first joints laigest. Internal footstalk of external double palpes one-jointed, with the apex 
somewhat abruptly acuminate, rounded and bearing the palpes. Anterior pair of legs equal, 
didactvle ; the other legs simple compressed (especially in the male), fifth pair shortest : nails 
bent, sharp and strong. Abdomen seven-jointed in both sexes. Shell avote-orbicular, orbicular- 
quadrate or transversely-subquadrate. Eyes thick, with short footstalks, inserted at a distance 
from each other in the front of the shell. 
All the Pinnotheres inhabit bivalve shells, and were supposed by some of the ancients to be 
consentaneous inmates with the animal, bound by mutual interest; the fable is beautifully told 
by Oppian, and is alluded to by Cicero *. 
Aristotle supposed them to act as centinels, and believed that they guarded the Pinna (the 
shell in which they were first observed) from the attacks of its enemies; Rondeletius and some 
other naturalists held the same opinion. 
The species are but little understood, and it is even probable that I may in some instances 
have considered the sexes as distinct species ; those which are described, however, have received the 
sanction ot my friend Mr. Montagu, who entertains the same opinions with myself on this difficult 
subject, and to whom my warmest thanks are due for the trouble and time which he has ever 
most kindly and willingly bestowed in giving me his opinion when it has been required. 
Pinna \ero, (sir. enim gracce dicitur,) duabus grandibus patula condiis, cum parva squi'la quasi societatem coit 
comparand! cibi. Itaque cum piscicuii pant in concham hiantem innalherint. turn admonita a squilla piuna niorsu 
“ t0mprimit conchas ~ Cic. de nat. Deor. Lib. 2. Sec. XLV11L ’ 
