40 Addis on E. Verrill, 



D. Exopodites on all the maxillipeds and legs, except rarely the last. 



Penaopsis. 



DD. No exopodites on the legs Parapencsus (restr.), extralimital. 



CC. No pleurobranchiae at the bases of either the fourth or fifth legs. 

 Epipodites lacking at least on the fourth and fifth legs ; exopodites 

 present on all the legs ; antennular flagella short Trachypenaus. 



AA. Dorsal carina crested and dentate. Anterior legs without exopodites. 

 Abdominal segments sculptured and carinated. A pair of slender 

 median subocular spines. Male orifices subcoxal. Pleopods unira- 

 mous. Subfamily Sicyoninae; genus Sicyoniu. 



Penaeus Fabricius (restricted). Large prawns. 



Penaus Fabr., Entom. Syst., vol. v, 1798 (pars). Desmarest, Consid. 

 gen., p. 224, 1825. Milne-Edw., Hist. Crust., vol. ii, p. 411, 1837 

 (pars). Stebbing, Hist. Crust, p. 214 (restricted). Bate, Voyage 

 Challenger, vol. xiv (restricted). Smith, S. I., on some Genera and 

 Species of Penaeidae, Proc. U. S. National Mus., vol. viii, pp. 170-190, 

 1885 (restricted). Report on Decapod Crustacea from Albatross 

 dredgings in 1884, p. [80], 1886. Rathbun, M. J., Crust, of Porto Rico, 

 p. loo, 1901. 



The rostrum is long and serrated on the upper margin, some- 

 times also on the lower margin. The perepods on legs of the first 

 three pairs have exopods and small equal chelae; the third pair of 

 legs are the longest. The outer maxillipeds or third gnathopods 

 are leg-like, elongated, and have an exopod. Podobranchiae are 

 lacking. Usually 18 pairs of gills. The eye-stalks are two- 

 jointed or three-jointed. The antennal flagella are not longer 

 than the carapace. The mandibles have a two-jointed palpus. 



Pleopods, except the first pair, have two thin foliate branches ; 

 those of the first pair, in the male, have a large, membranous 

 basal appendage known as the "petasma" or curtain; it is rudi- 

 mentary in the female. The female has a thelycum. 



Prof. Sidney I. Smitfc, in his important work on the Penatidce 

 (op. cit., 1886), gave the following additional characters for the 

 restricted genus Pen&us, as limited by him (type P. caramote). 

 Viz. : 



The antennular flagella are very short. The distal segment of 

 the mandibular palpus is much larger than the proximal one. It 

 is very broad and is not prolonged into a narrow tip. The 

 endognaths of the first maxillae are greatly elongated and seg- 

 mented. The endopod of the outer maxilliped is slender and com- 

 posed of four segments, and the exopod is lamellar and 



