PACHYCEPHALA. 21)5 



1. L^M ARGUS MURicATUs. Tab. XXXIV, figs. 3, 4. 



LiEMARGUS MUKICATUS, Kroycr, Tidsskrift, i, 487, t. 5, f. a, b, c, d. 

 — if. Edwards, Hist. Nat. Crust., iii, 475, 



t. 39, f. 2. 



Description. — The female of this little animal is about 

 ten lines, or nearly an inch in length, and of a light horny 

 colour. The carapace or cephalo-thorax is considerably 

 smaller than the rest of the body, and is studded all over 

 with numerous small prickly tubercles. The elytraform 

 plate and last thoracic segment are finely serrated round 

 the lower margins, and are both deeply notched. The 

 male is about half an inch in length. 



Hab. — On the Orthagoriscus 'molce, or short sun-fish, 

 W. Yarrell, Esq. 



Tkibe %— PACHYCEPHALA.'' 



In the animals belonging to this tribe, the head is 

 generally much smaller than in those of the preceding, 

 and has not the broad, flat, shield-shaped form that these 

 have, nor the lamellar plates on the front part, but is 

 generally rather thick and obtuse. 



The antenna3 are much longer than those in the 

 Peltocephala, and are composed of five and six, and even 

 more, articulations. The thorax varies in the different 

 genera, in form and in the number of articulations of 

 vs^hich it is composed. The mouth-apparatus is generally 

 less strongly developed in these genera than in the others, 

 and the conformation of the foot-jaws is much less regular. 

 The feet of the animals belonging to the Pachycephala 

 differ also from those organs in the Peltocephala. They 

 are not, as in these latter, attached to a basal joint, which 

 extends across the under surface of the thorax in the 

 shape of a broad plate, but have their basal joints detached 

 from each other. They are all parasitic, and when young 

 undergo a metamorphosis like the Cyclopidae. 



* Uoxi'C; thick, aud KnpaXii, head. 



