37 
bear small spiniform processes on their outer margin. In Spher. dispar (pl. 1X, fig. 3h) and 
in Spher. insignis (pl. X, fig. 1b and fig. 1c) the frontal plate expands in a most peculiar 
way. Seen from below, the head tapers very much towards the front, whereupon it dilates 
to an almost circular plate or a transverse oval with acute lateral angles; the sides and the 
front margin of the circular plate and the front margin of the oval project into a series of 
closely situated spiniform little processes; on the ventral side of the plate we see a chitinous 
ring, from the inner edge of which four processes run towards the centre; in S. dispar these 
processes do not meet, but form the surroundings of a cross-shaped space, whereas in S. insig- 
nis they meet in the centre, thus forming a cross, and dividing the space into four parts, 
(which perhaps are pierced with small holes). The purpose of this peculiar ring is un- 
known to me. 
The part surrounded by the protruding frontal and lateral borders frequently lies 
very deep, and where the lateral borders are high, sometimes, as in Spher. curtipes (pl .X, 
fig. 2f and fig.2¢), they hide the rostrum and the maxille, if the animal is seen from the 
side; as a rule a lateral view shows these organs in almost their whole, or in half of their 
length. Several males of the same species may show great individual difference in this 
point, whereas on the other hand, there are species, as e. g. Spher. curtipes, mm which the 
rostrum and the maxille are always partly invisible because of the height of the lateral 
borders, in other species again, as in Spher. microcephala (pl. VIII, fig. 2 ¢ and fig. 2h), the 
borders are so low, that the above-mentioned organs are always visible in nearly their 
whole length. 
The sub-median skeleton, which is found in all females and has been described as 
far as this sex is concerned, is also seen in all males, and in most respects shows a similar 
structure, but in most species of the genus Sphwronella it is produced into free processes. 
Three pairs of such processes may be found. ‘Those of the first pair are usually rather short 
and broad, sometimes rounded, in S. microcephala (pl. VIII, fig. 2 ¢ and fig. 2 h, i) pretty 
long, slender and pointed, being situated behind or below the basis of the maxille; some- 
times, as in S. elegantula (pl. Il. fig. 2f and fig. 2 @), they extend backward over the basal 
part of the maxillipeds. The second pair of processes are found most frequently, and may 
become much longer than any of the other two pairs; they proceed at a shorter or longer 
distance from each other between the maxillipeds, and are sometimes parallel, sometimes or 
mostly diverging. The third pair appears in very few species only, as in S. paradoxa 
(pl. ILI, fig. 4h and fig. 41), in S. Metopw and in S. Holbolli (both on pl. V.); they proceed 
between and a little behind the second pair and are much shorter than these ones. In the 
systematic description of the species I use the terms: first, second and third pair, in speaking 
of these processes. 
The Antennule are found in all species; in Sfenothocheres they are situated in front 
of and outside the antenne, in all other forms they are found on the lateral margins of the 
head, where these merge into the frontal margin. They are constructed much like those of 
