170 
IV. Choniostoma #. J. H. (1886). 
FEMALE. The body is somewhat flattened; seen from below, it is broader than 
long, nearly pentagonal, with rounded angles, one of which forms the centre of the posterior 
margin, and two on each side, whereas the anterior margin forms but a slight curve and 
is longer than the distance between the lateral angles on each side, and between the 
hindmost lateral angle and the posterior central angle. The head is situated on the 
ventral side a little behind its anterior margin, and the skeleton is transformed into a 
transverse ring-shaped frame which is considerably broader than long, and the anterior part 
of the frame, which forms the frontal border, may sometimes rise a little above the skin in 
front of it, whereas the remainder, or sometimes the whole frame, is on a level with the 
ventral plane. The frame surrounds a good-sized, thin-skinned area, in or a little behind the 
middle of which the rostrum and the mouth-appendages are found. The antennule are nor- 
mal, 3-jointed and inserted on the rg. The antenne are certainly 3-jointed and furnished 
with a terminal seta. The mouth is good-sized, the mouth-border of about average breadth. 
Maxillule well developed, with a long additional branch. Maxille powerful, constructed as 
in the typical species of Spheronella. Maxillipeds rudimentary, each consisting of two very 
small or quite diminutive joints. Trunk-legs and caudal stylets — where such are found — 
as in Spheronella. The genital area is more than twice as broad as it is long; the thickest 
chitine is found in the middle and along the lateral margins; the genital apertures are 
situated close together in the middle of the area, and close in front of them appear the 
orifices of the long sausage-shaped receptacula seminis, which are turned obliquely forward 
and outward. — No spermatophores have been observed. 
MALE. Unknown. 
OVISACS. They are always deposed freely, their shape is sub-globular, and as 
many as eleven or twelve may be found in one female. Hach ovisac contains an exceedingly 
great number, on an average at least one thousand, minute eggs (comp. my figures p. 47). 
LARVA. Is known of both species and is quite similar in structure to the larve 
of some of the species of Spheronella living in Amphipoda; the only differences are, that 
the cephalothorax is shorter and broader, and the spiniform sete at the posterior angles 
of the first abdominal segment longer, and especially thicker, than in any Spheronella 
known to me. 
POST-LARVAL DEVELOPMENT. ‘The pup found are described in detail above 
Die 
HABITAT. The branchial cavity of two species of the genus Hippolyte Leach 
belonging to the order Decapoda, and the presence of the parasite causes the part of the 
carapace which is situated above the intruder and its ovisacs to vault strongly, so as to 
form a large swelling, which as a rule is exactly similar to that caused by Gyge Hippolytes 

on p. 56 
