12 



on the thoracic legs (only in some species of Halipoms is there a rudimentary 

 podobranch on the 1st pair). Arthrobranchiae in a double series. 



II. ARISMINJE. No leaf-like appendage on the inner border of the basal 

 joint of the antennular peduncle. Exopodites are present on the 1st and 2nd 

 maxillipeds, but are usually absent or, if present, are of very small size, on the 

 thoracic legs. Podobranchise are present on the first two or three pairs of 

 thoracic legs. Arthrobranchia3 in a double series. 



III. SICYONIN.E. No leaf-like appendage on the inner border of the basal 

 joint of the antennular peduncle. No exopodites to any of the thoracic append- 

 ages behind the 1st maxillipeds. No podobranchige. Arthrobranchise in a 

 single series. 



Key to the genera and sub-genera of Peneidae of the Indian Necton. 



I. The inner border of the 1st segment of the antennnlar peduncle carries a 

 twisted setose scale that forms an incomplete inner wall to the orbit. 

 No podobranchiss on any of the legs : 



1. Antennular flagella cylindrical : 



i. The 2nd joint of the mandibular palp is vastly larger than 

 the 1st and forms almost the whole palp : the exopodites 

 of the external maxillipeds are large ... ... PENEUS. 



ii. The 1st joint of the mandibular palp is a good deal larger 

 than the 2nd : exopodites of the external maxillipeds 

 rudimentary or absent ... ... ... HAUPORUS. 



2. Antennular flagella thin, broad, compressed : (the 2nd joint of the 



mandibular palp much larger than the 1st : exopodites of the 

 external maxillipeds very short and slender) : 



i. The sub-foliaceous antennular flagella are truncated ... SOLENOCERA. 

 ii. The sub-foliaceous antennular flagella gradually taper to a 



lash ... ... ... ... ... PAUASOLENOCERA. 



II. The scale on the inner border of the 1st segment of the antennular peduncle 

 is absent or quite rudimentary. Podobranchiro are present on the first 2 

 or 3 pairs of legs : 



1. The outer (upper) antennular flagellum is extremely short, the 

 inner (lower) flagellnm is long : the 1st joint of the mandibular 

 palp is much longer than the 2nd, but though it is compressed and 

 broad, it is not foliaceous : 



i. No hepatic spine : rostrum dorsally 3-toothed (rarely 2-4 

 toothed) : 



a. The 3rd pair of legs have an epipodite but no podo- 

 branch, the 4th pair have no epipodite : 

 a. Cervical groove indistinct : the pleuro- 

 bvanchise in advance of somite xiv are 

 mere filaments or papilla? ... ARISTAEUS. 



ft. Cervical groove fine but conspicuous: the 

 pleurobranchiee in advance of somite 

 xiv, though small and slender, are 

 plumose and functional ... ... HEMIPENEUB. 



