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the masticatory part styliforin. Maxillae feeble, and generally divided into 2 seti- 

 ferous lobes. Botb pairs of raaxillipeds subcbeliforni, adapted for prehension. 

 Natatory legs, as a rule, well developed, with triarticulate rami. 



Remarks. The name "Siphonostoma" is here taken in a much more 

 restricted sense than is done by its proposer, Thorell, viz., to designate only a 

 section of semiparasitic Cyclopoida, in which the mouth, by the prolongation of 

 the anterior and posterior lips, has assumed a more or less suctorial character, 

 recalling that found in some of the true parasites, for instance in the Caligoida. 

 Yet the characteristic Cyclopoid appearance in all of them has been preserved, 

 and none of them are to be regarded as permanent parasites, as they have the 

 power to leave their hosts at will, and to move freely through the water by the 

 aid of their generally well developed natatory legs. Indeed, many of the forms 

 have hitherto only been found in such a free condition, though the structure of 

 the mouth organs evidently show them to be adapted for temporary parasitic habits. 



In the restriction here adopted, the present section answers fairly well 

 to the family Asterocheridce of G-iesbrecht. This family, which is included in his 

 great division Ampharthrandria, comprises several types, which are so widely 

 different, that in my opinion they cannot properly be combined within one and 

 the same family. Giesbrecht himself has also been aware of this difference, and 

 for this reason has established within the family Asterocheridce a number of so- 

 called sub-families. These I regard as true families, and their number will be 

 still somewhat increased. 



Fam. 4. Ascomyzontidae. 



Characters. Body Cyclops-like, with the anterior division more or less 

 dilated, the posterior narrow and attenuated. Anterior antennae generally slender 

 and composed of a great number of articulations, the outermost of which form 

 a distinctly-defined terminal part, the joint preceding this part being constantly 

 provided with a very fully developed sensory filament; same antennae in male 

 more or less distinctly hinged, with the number of joints somewhat reduced. 

 Posterior antennae moderately strong, 4-articulate, 1st, or coxal, joint short, the 

 2 succeeding ones more or less prolonged, and forming together a geniculate bend, 

 last joint small, carrying on the tip a slender spine accompanied by 2 or 3 short 

 bristles, one of which issues from a knob-like prominence of the anterior edge. 



