290 PSEUDEUPHAUSIA LATIFRONS. 
the two outer pairs are nearly as in the preceding stage, but the inner pair are 
almost twice as broad. 
Length of the specimen described 3.7 mm. 
Remarks.— By the distally broad and emarginate frontal plate the larvae 
of Nyctiphanes and Pseudeuphausia differ strongly from those of all other 
Euphausiacea. The above-described larvae were chosen among a good number 
of larvae and young and adult specimens from Sta. 4655, Nov. 12, 1904, Surface. 
Young specimens with the frontal plate distally emarginate and the character- 
istic lobe of first antennular joint high but not yet fully developed have been 
described on p. 228. This lobe begins to protrude conspicuously in a specimen 
measuring about 4.5 mm., and in this specimen the telson has nearly acquired 
its final shape. Specimens measuring 4.5-5 mm. are therefore easy to determine 
by aid of the lobe mentioned as Nyctiphanes, for Pseudewphausia latifrons 
G. O. S. does not possess such a high protuberance; the differences between 
larvae of Nyctiphanes simplex still without the antennular lobe and stages of 
Pseudeuphausia of the same size are pointed out below. 
The larvae described show that they acquire a rather considerable size before 
the appendages are half developed and before the end of the telson begins to 
lose its larval armature, though adult specimens are rather small. The distal 
process of first antennular joint remains very long until the specimens are con- 
siderably more than half grown, and the dorsal carina of the carapace is very 
small even in the youngest larva described. 
Pseudeuphausia latifrons G. O. Sars. 
Plate 12, figs. 4a—4b. 
As stated above, Dr. Agassiz collected at the Fiji Islands a number of speci- 
mens, among which are a few larval forms; and from the ‘‘Siboga” I have 
several larvae in the Furcilia- and Calyptopis-stages. And they are mentioned 
chiefly for comparison with those of Nyctiphanes simplex. 
The larvae of Pseudeuphausia differ from those of Nyctiphanes simplex 
especially in three features, viz. they are, when chosen in the same stage, con- 
siderably smaller, their antennular peduncles are more slender and the frontal 
plate is not only more deeply emarginate, but the emargination is not rounded, 
but angular at the middle. The anterior and the posterior parts of the youngest 
Agassiz specimen are rendered in figs. 4a and 4b, and a view on these figures 
shows that the antennular flagella and the telson are considerably more devel- 
oped than in the above-described specimen in last Furcilia-stage of Nyctiphanes, 
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