MEDESICASTE ASELLINUM. 



1900. Oralien aseWnus T. Scott. (112) p. 163, pi. vii, figs. 16-18. 

 1906. Medesicaste triglurum Brian. (21) p. 94. 



Female. Head small, subglobose, situated at the 

 end of a tolerably long and slender neck, rounded in 

 front, and with each side expanded into rounded lobes, 

 the whole forming a bulb-like extremity usually in- 

 closed in the tissues of the host ; this anterior part 

 furnished with two pairs of antennas, which are 

 small and have hook-like extremities. The neck, 

 where it joins the posterior portion of the body, 

 slightly enlarged. This posterior portion of the body 

 tolerably large and robust and divided by a deep 

 transverse constriction into two subequal parts ; the 

 front part appearing to constitute the thorax Avith its 

 appendages, and the lower the genital segment, the 

 antero-lateral corners of which extend outwards into 

 angular projections ; the lateral margins of this lower 

 segment slightly arcuate, converging clistally, and 

 forming two small postero-lateral lobes, separated from 

 each other by a small median sinus, best seen from 

 the ventral aspect. Abdomen very small, occupying 

 the space between the postero-lateral lobes. 



Both pairs of antenna? small, and situated on the 

 subglobose cephalic segment as described above. 

 Mandibles stout, falcate, and with their margins 

 fringed with numerous small teeth as in Ckondra- 

 (nnthus; maxillae and other mouth-appendages also 

 somewhat similar to those in Chondracnnthus. Thoracic 

 legs two pairs, very rudimentary. Colour pale red. 

 Egg-strings nearly as long as the body and containing 

 many ova. Length exclusive of egg-strings about 7 mm. 



Male. Extremely small and similar in structure to 

 the male of Clwndracanthus. 



Habitat. Parasitic on the gills of Trinla spp., 

 Gadus spp. ; also on the plaice (Pleuronectes platessa) 

 and other fishes, captured in British waters, frequent. 



A somewhat variable species, and apparently widely 

 distributed. 



