199 



Bopyroides hippolytes, (Kreyer). 



(PI. LXXXXV, fig. 2). 

 Bopyrus hippolytes, Krayer, Gronlands Amphipoder, p. 78, PI. 4, fig. 22. 

 Syn.: Gyge hippolytes, Sp. Bate & Westw. 



Specific Characters. — Body of fully grown female broadly oval, rather 

 asymmetrical, being curved to the right or left, according to its place on the 

 host; dorsal face much flattened and very smooth. Cephalon almost semicircular 

 in form, and deeply immerged within the mesosome, frontal edge nearly straight, 

 lateral corners obtusely pointed. Segments of mesosome firmly connected, with 

 the lateral parts perfectly smooth, contiguous, and without any marginal indenta- 

 tions. Metasome comparatively short, its median length scarcely exceeding 1 / s of 

 that of the preceeding part of the body, sutures between the segments much 

 curved and distinct also in the middle of the dorsal face, epimeral plates con- 

 tiguous, truncate at the tip, last segment likewise truncate. Male very slender, 

 linear, 4 times as long as it is broad, segments of mesosome very sharply marked 

 off from each other, metasome forming an undivided obtusely conical piece. 

 Colour of female whitish, with the incubatory plates dark violet. Length of 

 female reaching to 11 mm., that of male to 2 x /2 mm. 



Remarks. — This form was first described by Kreyer as Bopyrus hippo- 

 lytes, and was subsequently referred by Sp. Bate and Westwood to the genus 

 Gyge of Cornalia and Panceri. It must, however, unquestionably find its place 

 within the genus Bopyroides of Stimpson, and it is indeed somewhat questionable, 

 if the species of Stimpson, B. acutimarginata, is not identical with the North 

 European form. In its general appearance and its mode of infesting its host, the 

 female of this Bopyrid bears a great resemblance to Bopyrus squillarum, but may, 

 on a closer examination, be easily distinguished by the distinct segmentation of 

 the metasome, and by the want of true pleopoda, the latter being replaced by 

 very slight, fleshy ridges. The male, moreover, distinguishes itself by its very 

 slender form and the complete fusion of the segments of the metasome. 



Occurrence. — I have met with this form along the whole Norwegian 

 coast, from Vads0 to the ChristianiaFjord. It is found parasitic in the branchial 

 cavity of 3 different species of the genus Spirontocaris Sp. Bate (Hippolyte 

 Kroyer) viz., S. polaris, in which species it was first found by Kr0yer, 8. 

 spinus and S. securifrons. I have very carefully compared specimens from all these 

 3 species, and have pot been able to find any difference between them. When 



