284 THE SCHIZOPODA. 



which, for the others, must always be very difficult, as frequently it will be next 

 to impossible to find specific characters for every stage of every species. As the 

 number of species of the genus Euphausia collected by the Agassiz expedition 

 1904-1905 is fourteen, and it may be expected that larvae of the majority of these 

 species exist in the material, it will instantly be seen that to solve the difficulties 

 connected with the endeavour to refer the older larval stages to their proper 

 form and then in a similar way to proceed from older to younger stages would 

 have been in most cases at least very great and sometimes or frequently impos- 

 sible. Under such circumstances I thought it better not to make a hazardous 

 attempt to work out the material of these larvae, with the exception of some few 

 presenting a somewhat peculiar aspect and belonging to a single species. But 

 I thought it useful and safer to describe a number of larvae of five other genera, 

 hoping thereby to give an addition of some little importance to our knowledge 

 of the larvae of this order, especially as I am able to refer most of these larvae 

 to the species in question. 



THYSANOPODA sp. (T. monacantha aff). 

 Plate 12, figs, la-lg. 



A. Fir&l Furcilia-Stage (figs. la-Id). — The frontal plate (fig. lb) very 

 long, nearly as long as broad at the base; its lateral margins proximally concave, 

 more distally convex and then almost straight to the slightly acuminate, acute 

 tip; the upper surface a little concave longitudinally. — The carapace has a 

 fine denticle on the lower margin somewhat before its posterior end (fig. la); 

 seen from the side a short, but somewhat high keel, including the dorsal organ, is 

 seen on the upper margin considerably nearer to the posterior margin than to 

 base of the frontal plate. — The eyes are large, yellow with the central part black, 

 but they do not reach beyond the sides of the carapace (fig. lb), as their stalks 

 are short. — The antennular peduncles short and very robust; first joint ex- 

 tremely broad, with its distal outer process reaching the end of third joint and 

 furnished with fine spines on the inner margin; second joint broader than long 

 with two very long, plumose setae on the inner margin; third joint nearly half 

 as long again as the second and a little longer than broad, with terminal setae 

 and three very long, plumose setae on the inner margin; botli flagella are one- 

 jointed, the upper much shoi-ter and thinner than the lower which is a little 

 shorter than the third peduncular joint. — The antennae (figs, la and lb) with 

 both rami one-jointed and terminating in a bundle of extremely long, plumose 



