88 



of legs with the distal joint oblong oval in form, and provided with only 2 apical 

 setse. Ovisacs of moderate size, oblong in form, and rather divergent. 



Male much smaller than female, and exhibiting the usual sexual differences. 



Body in both sexes highly pellucid and nearly colourless, with only a 

 very faint yellowish tinge. 



Length of adult female about 0.90 mm., of male 0.70 mm. 



Remarks. This form was described under the above name in the year 

 1859 by Thorell as the type of his genus Ascomyzon. Giesbrecht thought it 

 necessary to change the specific name Lilljeborgi^ because this name was given 

 at a somewhat earlier date by Boeck to another species of this genus. If, how- 

 ever, my proposal to name Boeck's species as above, be accepted, a change in 

 the name of Thorell's species will be avoided. 



The most prominent character distinguishing the present species is 

 undoubtedly the exceedingly long and slender siphon, for which reason Giesbrecht 

 proposed to name it A. siphonatus. The species which comes nearest to it in this 

 respect is the Neapolitan form A. stimulans Giesbr., in which the siphon is said 

 to extend almost to the insertions of the 4th pair of legs. 



Occurrence. Thorell found this form in the branchial cavity of Corella 

 paralellogramma, and I have myself taken it not infrequent at Ris0r, south coast of 

 Norway, from the same Ascidian. Two female specimens were also found among 

 dredged material procured at Grimstad, somewhat farther west. 



Distribution. Bohusliin (Thorell). 



51. Ascomyzon Boeeki, (Brady). 



(PI. LIV). 

 Artotrogus Boeeki, Brady, Monograph of British Copepoda, Vol. Ill, p. 60, PI. XCI. figs. 1 9. 



Specific Characters. Female. Anterior division of body rather broad and 

 expanded, with the cephalic segment very large and evenly rounded in front; 

 lateral parts of the succeeding segments rounded off at the end. Tail compara- 

 tively short, scarcely exceeding in length l / 3 of the anterior division; genital 

 segment moderately dilated and occupying more than half the length of the tail; 

 anal segment scarcely longer than the preceding one. Caudal rami short, about 

 as long as they are broad; apical setse not much elongated. Anterior antennae 

 nearly as long as the cephalic segment, and composed of 20 articulations, all 3 

 joints of the terminal part being well defined. Posterior antennae about as in 

 A. Lilljeborgi. Oral cone, as in that species, terminating in a narrow siphonal 

 tube, which however is considerably shorter, only extending a little beyond the 



