290 PSEUDEUPHAUSIA LATIFRONS. 



tlic two outer pairs are nearly as in the preceding stage, i)ut the inner pair are 

 ahnost twice as broad. 



Length of the specimen described 3.7 nim. 



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 lar\ae 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 tlistally emarginate and the character- 

 istic lobe of first antennular joint high but not j-et 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 Pseudeuphausia 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 ai;)pendages 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 Fiu'cilia- 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, 



