yy ll Part III.— Twenty-third Annual Report 
Fam. DICHELESTIIDA. 
Genus Dichelestium, J. F. Hermann (1804). 
Dichelestiwm sturionis, Hermann. PI. v., figs. 17-24; pl. vi., figs. 1-6. 
1804, Dichelestium sturionis, Herm., Mem. Aptérologique, p. 
125, Tab. v., figs. 7-8. 
1837. Dichelestium sturionis, Kroyer, Naturh. Tidsskr., 1st B., 
p. 299, Tab. i1, figs. 5 and 5a (9). 
Description of the Female.—The length of the female represented by 
the drawing (pl. vi, fig. 1) is 17°8mm (nearly # of an inch). Body 
elongated and narrow ; cephalic segment nearly as broad as long, widest 
behind the middle, sides angulated, truncate, and obscurely trilobed in 
front. Thoracic segments four, first and second subequal, length equal to 
about half the breadth, and narrowly rounded at the sides; third seg- 
~ ment rather shorter than the one which follows, and each with a shallow 
transverse suture that divides it into two slightly unequal portions. 
Genital segment narrow, and about one and a half times the length of 
the one which immediately precedes it ; the ultimate segment ovate, small, 
being scarcely half the length of the genital segment. Furcal joints 
short. Ovisac long and slender (pl. vi., fig. 1). 
Antennules short, slender, and apparently composed of eight subequal 
joints (pl. v., fig. 17). 
Antenne robust, extremities chelate, and forming powerful grasping 
organs (pl. v., fig. 18). 
The mandibles resemble those of Caligus or Lepeoptheirus very closely, 
but differ in having a stouter basal part, and in the long slender 
rod-like portion being only three-jointed, the last joint being coarsely 
serrated on the inner edge (pl. v., fig. 20). 
Maxillee small; two-branched ; primary branch stout, tapering distally 
and furnished with two slender apical sete ; secondary branch very small 
(pl. v., fig. 21). 
The first maxillipeds appear to be three-jointed. The first joint, 
which is large and tolerably dilated, is about as long as the next two 
combined ; the distal end of the second joint is fringed with short 
bristles, and the end joint, which is very small, is furnished with a short 
terminal claw, and a few small marginal spines are shown in the drawing 
(pl. v., fig. 22). 
The second maxillipeds, short, very robust and strongly chelate (pl. v., 
fig. 23). 
The thoracic legs are short and stout, The first and second pairs are 
two-branched. The branches of the first are indistinctly two-jointed, and 
the outer branches are furnished with a small spine on the outer distal 
angle of the first joint, while the end-joint bears five moderately stout 
spines on its rounded extremity; the inner branches bear each two 
terminal spines (pl. vi., fig. 3). The second pair are rather more dilated 
than the first, and both branches are similarly armed (pl. vi., fig. 3). 
The fourth pair is composed of a single uniarticulate branch in the 
form of an elongated lamelliform plate which bears a few minute teeth 
round the distal end (pl. v., fig. 24). 
The male, which resembles the female, but is considerably smaller, 
being scarcely half an inch in length, and the genital segment is also 
proportionally shorter (pl. vi., fig. 2); there is also a difference in the 
second and fourth pairs of thoracic legs, as shown in the drawing (pl. 
cae uae 5 and 6). In other respects the male is very similar to the 
female, | 
