THYSANOPODA PECTINATA. 221 
than broad and distinctly divided by a constriction into an upper somewhat 
small and a lower, conspicuously broader and much higher area; the colour is 
dark brown. The antennulae have the process from the outer distal angle of 
first joint proportionately longer than in the adults; the lobe from the same 
joint is only a little expanded towards the end, with about six terminal teeth 
which are shorter than in the adults; the lobe from second joint is also shorter 
than in the adults—— Two such specimens are at hand. 
Remarks.— This species is easily distinguished from all other forms of the 
genus by the terminal row of spiniform teeth on the lobe from first antennular 
joint. 
During a long time I considered the specimens from the Pacific as belong- 
ing to a separate and new species, because the shape of their frontal plate differs 
materially from that of my single female specimen of T. pectinata from the 
Atlantic, and this specimen and that recorded by Ortmann are much larger 
than any specimen in the rich Agassiz material. But in the winter 1910-1911 
I obtained from Monaco several recently captured specimens of 7. pectinata, 
among them two adult males; the examination of the copulatory organs of 
these specimens did not reveal any difference from those from the Pacific, and 
I was unable to detect any other difference between the animals from the North 
Atlantic and those from the Pacific than the anteriorly broader and much more 
obtuse frontal plate in the former together with their much larger size. The 
result of study was that I must consider the Pacific specimens as a smaller 
local form or variety of T. pectinata—— Nematoscelis microps G. O. 8. shows also 
local variation in the shape of the rostrum in both sexes and especially in the 
males, as is seen by comparison of specimens from the Atlantic, the Indian 
Archipelago, and the East Pacific (comp. the ‘‘Siboga” Report and my notes 
on NV. microps in the present paper). 
The young specimen just described is interesting. I have stages inter- 
mediate in size and development between that small specimen and the adults, 
and that it belongs to this species is easily seen from its lobe of first antennular 
joint. The oblong, divided eye, the shape of the frontal plate and the existence 
of a denticle on the lateral margins of the carapace agree completely with the 
features found in very young specimens of 7. orientalis H. J. H. belonging to 
the same group of the genus. That Illig’s Parathysanopoda foliifera has been 
founded on a young specimen of T. pectinata is easily seen from his description 
and figures; the specimen, which measured 15 mm., was captured in the Atlantic, 
and as the adults from this Ocean are as a rule much larger than those from the 
