PINNOTHERES. 
PINNOTHERES. Latreille, Bosc. 
a 
CANCER. Linn., Gmeil., Penn. 
ALPHAUS. Daidorff. 
Antenne externe setacex, brevissime, (articulis tribus primis majoribus,) in oculorum cantho 
interno inserte. , 
Pedipalporum geminorum externorwn caulis internus uni-articulatus ad apicem subabrupte 
acuminato-rotundatus, palpigerus. 
Pedum par anticum zxquale; paria 2, 3, 4, et 5 simplicia, (maris presertim) compressa, pari 
quinto breviore: Ungues arcuati, acuti, validi. 
Abdomen in utroque sexu 7-articulatum. 
Testa ovato-orbiculata, orbiculato-subquadrata aut transverse subquadrata. 
Oculi crassi pedunculo brevi, in fronte inserti inter se dissiti. 
External antenne setaceous, very short, inserted at the internal corner of the eye, the three 
first joints largest. Internal footstalk of external double palpes one-jointed, with the apex 
somewhat abruptly acuminate, rounded and bearing the palpes. Anterior pair of legs equal, 
didactyle; 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, erbicular- 
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 suppesed by some of the ancients to be 
consentaneous inmates with the animal, bound by mutual interest; tle 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 reecived the 
sanction of 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 vero, (sic enim grecé dicitur,) duabus grandibus patula conchis, cum parva squilla quasi societatem coit 
“comparandi cibi. Ttaque ciim pisciculi parvi in concham hiantem innativerint, tum admonita 4 squilla pinna morsu, 
“ a + 1“ . . “@ i 
comprimit conchas,”” Cic. de nat. Deor, Lib. 2,.Sec. XLVIII. 
