OF FISH OBTAINED AT PLYMOUTH. 161 



CHONDEACANTHINA. 



Chondracanthus, De la Boche. 



(1) Cephalothorax not separated from the abdomen by a long thin 

 neck. (2) »ont end of the body neither thicker nor more slender 

 than the posterior part. (3) Posterior antenna? in the form of hooks. 

 (4). Cephalothorax without processes. (5) Abdomen compressed with 

 concave sides, or with elongated lobes. Behind the second maxillipedcs 

 are two pairs of lobed processes, representing the thoracic limbs. 



{a) Two small horns at the posterior angles of the thorax. 



1. Chcnulracantlms cornutus, Muller. A great number of specimens 

 were taken from the gills of the Plaice, P. jplatessa, Flounder, P. Jicsiis, 

 and P. megastoma. They differed very much in size, being small and 

 especially abundant in the Flounder. The male was almost invariably 

 found fixed on the abdomen of the mature females, by means of 

 its strong, hook-like posterior antennae. 



2. Chondracanthus solea^, Kroyer. Found in the gill cavity of Solea 

 vulgaris, but not common ; male like the preceding. 



3. Chondracanthus clavatus, n. s}^* Found only on the gills of 

 P. microceplmlus. 



(b) A number of supplementary lobes on the sides, none on the 

 middle line. 



4. Chondracanthus triglcc, Blainville {G. asscllina, Linn). These were 

 plentifully taken from Trigla gurnardus, T. cuculus, and T. hirundo. 

 The whole anterior portion of the head, and so-called neck, is buried in 

 a ileshy mass in the substance of the gill, the thoracic portion only 

 showing. 



5. Chondracanthus merluccii, Holten. Taken from the mouth of Gaelics 

 merluccius, and is very common ; in no fair-sized hake have I ever 

 found it absent. Great numbers are often found together, large areas of 

 mucous membrane being destroyed. The very large hooks of attach- 

 ment (the second antennae) being deeply buried, strong muscles are 

 inserted into the bases of these, both for abduction and adduction, 

 so that one would gather that the animal is able to relax its hold, 

 and probably move from place to place. The male resembles closely 

 that of C. cornutus; in fact, no matter how varied the form of the 

 female in this genus, the males are perfectly distinctive. It was 

 also noticeable that one female would often have more than one 

 male attached, usually to the abdomen. At times as many as five 

 or six would be found fixed on to the various parts of the animal. 

 Occasionally young Caligidce were also present as secondary parasites. 



* See former note, p. 156. 



