the Mouth in Sucking Crustacea. 9 



occurs not unfrequently in the Sound and along the north 

 coast of Zealand. It was already known to Slabber, and was 

 described some years ago by Van Beneden (" Rech. sur les 

 Crustaces de Belgique," Mem. d. I'Acad. Beige, xxxii. p. 88, 

 t. 15) as Slahherina agata, but is doubtless the same species 

 that Leach described as Eurydice ^ulchra. Van Beneden re- 

 fers it to Idothese. 



The mandibles are destitute of grinders ; but their prehen- 

 sile part is, on the contrary, extraordinarily large, shaped like a 

 flat cup, the outline being almost quadrangular, the outer 

 corner pointed, the whole inner edge finely sharpened, hard as 

 glass, undulato-dentate, the inner corner drawn out into a 

 long dagger-like peg. The inner lobe is fixed closely under 

 the outer lobe, large, membranaceous, divided into two lobules, 

 of which the foremost is entire and covered with setaj in Ciro- 

 lana^ but digitilobate in Eurydice ; whilst the posterior lobule 

 in both genera is cultelliform, with a close row of pointed thorns 

 along the inner margin, which gives to the lobule the appearance 

 of a tenon-saw. The stem of the mandible is long, the palpus 

 slender, and, when not ^ased, placed in a groove round the large 

 labrum and the small clypeus, with the last joint slung round 

 the root of the posterior antenna. The first pair of maxillae 

 possess two lobes coalescing with the stem ; the inner lobe is 

 much abbreviated and has three cylindrical slender append- 

 ages, which in Cirolana are verticillato-spinulous towards the 

 apex, and furnished with a hard thorn-shaped terminal joint, 

 but which in Eurydice are soft, pointed, and hairy ; the outer 

 lobe is also rather short, particularly in Cirolana^ somewhat 

 arched inwards (fig. 3, a:-), powerful, the apex armed with a 

 bundle of long, exceedingly hard, and pointed thorns, groups 

 of similar thorns occuiTing all along the inner margin, which, 

 in Eurydice^ are much elongated and in part spinulous on the 

 inner side. The second pair of maxillae (fig, 3, a;*) are small, 

 their inner lobe very short, with feather-like setee and hairy 

 membranaceous digitiform appendages ; the middle lobe and 

 palpus are represented by a pair of uniform pointed leaflets. 

 The maxillipeds (fig. 3, px) have oval hinges, small stem, 

 rudimentary lobes, and fully developed, slender, flat palpus. 

 The forehead and clypeus are, in Cirolana, trapezoid, flat, in 

 Eurydice vaulted, the frontal cone protruding between the first 

 pair of antennaj (fig. 3 a,/) . 



Cirolange represent, no doubt, the highest development of 

 the Crustacean type amongst Isopoda. The outer lobes of 

 their mandibles are built exactly on the same plan as the car- 

 nassial teeth of mammalia. They are furnished with pegs to 

 be driven into the body of the victim, one from either side. 



