164 



Part III. — Eighteenth Annual Report • 



Cho?idracanthus soleae. Ten species are recorded in the sequel, but one of 

 them is somewhat doubtful and apparently undescribed. 



Chondracanthus comutus (Midler). (PI. VIL, figs. 19-31.) 



1776. Lerncea cornuta, Miiller, Zool. Dan., vol. i., pi. 33, fig. 6. 

 1850. Lernentoma cornuta , Baird, op. cit., p. 328, PL XXXV., 

 fig. 2. 



This species, as represented by the figure in Dr. Baird's " British 

 Eutomostraca," has the genital segment of a cylindrical form and without 

 any marked constriction in the middle ; and in his description of the 

 species Dr. Baird makes no allusion to any constriction of the posterior 

 " two-thirds " of the thorax ; had any constriction been observed, as con- 

 spicuous as it is, for example, in Chondr 'acanthus soleoe or Chondracanthus 

 flurce, he would very likely have referred to it. Moreover, the figures of 

 the same species by Nordmaim* and Kroyer,t though showing a slight 

 constriction of the thorax, agree fairly well with that of Dr. Baird. 



Specimens agreeing in their general appearance with Dr. Baird's figure 

 of Chondracanthus comutus, except that they exhibit a slight constriction, 

 as shown in the figure by Nordmann, have been found on the plaice, 

 Pleuronectes platessa, and the common flounder, Pleuronectes flesus. I 

 find on the plaice two forms of the Chondracanthus ; the more common 

 one (represented by figure 19) is the smaller of the two, and is also 

 proportionally broader. The specimen of this form represented by the 

 figure referred to measured 5'8mm., exclusive of ovisacs. The antennules 

 of this specimen were considerably dilated, and showed little structure. 

 The antennae were furnished with strongly-hooked terminal claws, while 

 the mandibles were moderately stout and tapered towards the end, where 

 they became somewhat attenuated. The anterior foot-jaws had a moderately 

 stout basal part, but the end-joint was more slender and was serrated on 

 the inner edge (fig. 23). 



The male of this form, which is very small, is represented by figure 

 24 ; it measured scarcely the half of a millimetre in length ; the abdomen, 

 which appeared to be distinct from the thorax, was more or less segmented. 



A specimen of the less common and more elongated form is represented 

 by figure 27 ; it measured nearly 7 millimetres in length. The posterior 

 portion of the thorax in this form is long and narrow, and slightly 

 constricted in the middle ; the antennules (fig. 28) appear to be scarcely so 

 robust as in the smaller form, but the mandibles and other appendages do 

 not seem to differ much. 



Habitat. — The smaller form has been obtained on plaice from the Firth 

 of Forth, Firth of Clyde, Moray Firth, and at Aberdeen Fish Market, The 

 larger form was found on the gills of a plaice in the collection of fishes 

 in the Laboratory at Bay of Nigg, but the locality where this plaice 

 came from is not stated on the label. 



Chondracanthus annulatus, Olsson. (PI. VII., figs. 46-51.) 



1867. Chondracanthus annulatus, Olsson, Prodr. Faunae Copep. 

 Parasit. Scand., vol. v., p. 30, PI. II., figs. 13-15. 



A number of specimens of this Chondracanthus were obtained from the 

 gills of a large grey skate, Raia batis, caught in the North Sea and landed 

 at the Fish Market at Aberdeen, June 30th, 1899. 



In this species the body is elongate, moderately narrow, and cylindrical 

 in form ; it is about four times longer than broad, and not much 



*Mikrogr. Beitr., vol. ii., PI. 9, fig. 5. 



fNaturh. Tidsskr., R. iii., vol. 2, PI. 13, fig. 7 (1864). 



