32G AMPUIPODA NORMAMA. 



Fam. 3. PLATYSCELID^. 



Typiiip^t:, Damt, U- S. Explor. Expcd.yt. 1442. 



Spciicc liati; Brit. Assoc. Report, 1855 ; Synopsis, SfC, Ann. Nat. 

 Hist. Feb. 1857. 

 Hyi'KRINES anormales, M.-Edivards, Hist, des Crust, iii. p. 94. 



Cephalon round. Eyes large. Antennae attached to the inferior 

 surface. Epistoma proboscidiform ; oral appendages rudimentary. 

 Gnathopoda complexly subchclate. First two pairs of pereiopoda 

 simple ; two succeeding pairs ha^'ing the basa largely dilated ; fifth 

 pair imperfectly developed. Posterior pleopoda foliaceous. 



The name TypMs, given to a genus in this family, having been 

 replaced by another, that of the family must necessarily be changed ; 

 I have therefore chosen the name of a genus which I have had the 

 opportunity of examining most, and which tj'pifies tho most con- 

 spicuous character in the family. 



This family coincides with the first two di\isions of Milne-Ed- 

 wards's HTpiniNfis anormales, and with the first two of Dana's 

 family TrpniDiE. 



Edwards and Dana have separated this family into two divisions, 

 exclusive of Oxycephalin^, corresponding with Typhin^e and Pro- 

 NOiN-E ( Dana) ; but these divisions appear to me to run so gradually 

 into each other, that it is difficult to say where the one ends and the 

 other begins. 



1. THYROPUS. 



Tj-phis, Risso, Cnist. de Nice, p. 122, 1816. 



Edtcards, Ann. des Sc. Nat. xx. p. 395 ; Hist, des Crust, iii. p. 94. 

 ThjTopus, Dana, U. S. Explor. Exped. p. 1012. 



Cephalon transversely oval. Pereion broadly distended. Pleon con- 

 siderably narrower than the pereion. Eyes lai'ge. Superior an- 

 tenna3 short. Inferior antennae long, consisting of five joints, 

 which inflect upon one another when folded and hid beneath the 

 cephalon. Gnathopoda complexly subchelate ; carpi having the 

 infero-anterior angle anteriorly produced to antagonize with the 

 extremity of the dactyla. First two pairs of pereiopoda slender, 

 cylindi-ical : third pair having the basos considerably dilated; 

 ischium subapically articulated at the posterior margin : fourth 

 pair having the basos dilated to a greater extent than the previous 

 pair, and having tho ischium articulated near the middle of the 

 posterior margin : fifth pair having the basos short, scarcely dilated ; 

 ischium articulating at the apex ; the other joints not developed. 

 Three posterior pairs of pleopoda having the rami foliaceous and 

 membranous. 



In consequence of the name Ti/jyhis having been given to a genus 

 of Mollusca by Montagu prior to the date at which llisso named this 

 genus, I have adopted Dana's synonym. 



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