of the Fishery Board for Scotland. 259 



of cephalo-thorax and abdomen closely beset with minute papillae, of 

 which fig. 18 is an enlarged representation. 



Male. — Body similar to that of the female but smaller (1'3 mm.). 

 Anterior antennas eight-jointed ; the proportional length of the joints are 

 as in the formula 



10 • 22 • 5 • 8 • 3 • 8 • 5 • 5 . 

 1 • 2-3-4 < 5-6-7'8 ; 



distinctly hinged between the sixth and seventh joints, and indistinctly 

 between the third and fourth. The fifth joint, which is very short, bears 

 a long olfactory filament. The posterior antennae, mouth organs, and 

 first pair of swimming feet as in the female. The last joint of the outer 

 branches of the second pair of swimming feet bears at nearly right angles 

 a long curved appendage closely resembling the blade of a reaping-hook, 

 and setose on the inner margin (fig. 13). The basal joint of the inner 

 branches of the third pair is furnished internally with a long slender pro- 

 cess, which extends beyond the extremity of the branch, and is armed on 

 the inner margin near the distal end with two barb-like teeth. The fourth 

 and fifth pairs as in the female, except that the fifth is rather smaller and 

 furnished with fewer setae. The abdomen five-jointed ; the posterior mar- 

 gin of the first abdominal segment bears a foliaceous appendage armed 

 with one long and two short, stout setae. Caudal stylets and setae as in 

 the female. 



Habitat. — Off St Monans, Firth of Forth, in 14 to 15 fathoms water ; 

 bottom clean course sand. Not uncommon. 



This interesting Copepod, which was described by Professor Brady in 

 his monograph of the British Copepoda in 1880, is apparently local in its 

 distribution, and is probably rare as well as local. The generic and 

 specific descriptions given in the monograph were prepared from the 

 examination of one specimen only — a female — and, as pointed out by 

 Professor Brady, both descriptions were necessarily somewhat incomplete. 

 Having some time ago in a single haul with the dredge secured a con- 

 siderable number of specimens including both males and females, the 

 opportunity was taken advantage of to make a careful examination of 

 both sexes so as to gain some knowledge of the affinities of the species. 

 In the monograph alluded to Cylindropsyllus was provisionally placed 

 among the Poecilostoma because of its apparently close relationship to 

 that group, but as the structure of some of the mouth organs had not 

 been satisfactorily made out no distinct place in the classification was 

 assigned to it. 



By the careful dissection of a number of specimens I have been able, 

 with the assistance of my son, to prepare a fairly complete description, 

 with a set of drawings, of the more important and characteristic append- 

 ages that distinguish Cylindropsyllus loBvis from other Copepoda. It will 

 be observed by referring to the description and drawings that there are 

 one or two characters which render the position of Cylindropsyllus among 

 the Poecilostoma untenable. These are the distinctly hinged male anterior 

 antennae, the presence of a secondary branch on the posterior antennae, 

 and the form of the mandibles, — characters which indicate a closer 

 affinity with the Harpacticidce than with either the Poecilostoma or the 

 Siphonostoma. If, on the other hand, the appendages of the peculiar 

 organ described as situated anterior to the mandibles be sucking disks, 

 the position of Cylindropsyllus in the classification would be somewhat 

 anomalous, as these appendages would indicate a tendency towards para- 

 sitism in this Copepod, — a tendency suggested by Dr Brady. No indication 

 of parasitical habits has, however, been observed hitherto in any of the 

 specimens obtained. 



