1886.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 319 



Of the three priucipal pairs of mouth organs, one pair is in advance 

 of the mouth opening and two pairs back of it, while on each side there 

 is a small palpus, terminating posteriorly in two sharp spines. The 

 organs of the first pair are rather slender, curved, and serrated on both 

 margins. Of the second pair, the terminal joint is slender, very slightly 

 curved, and tapers gradually to a sharp i)oint. The posterior margin 

 is armed with about ten acute spines, arranged in a single regular 

 series, extendiug from the tip to beyond the middle. The hinder pair 

 are comparatively very large, and capable of considerable extension 

 backward. The basal joint is very broad, the median joint of moderate 

 size, the terminal joint small, broad at the base, and rai)idly narrowing 

 to a slender distal end, terminating in a rather acute point- 



Arrangement of mouth parts in Chondracanthus galeritus. 



The thoracic appendages are comparatively small and divided at the 

 outer ends, for slightly more than half their length, into two subequal 

 portions, which are stout at the base and taper rapidly to sharp or 

 slightly rounded tips. The first pair originate just back of the head, 

 and are much smaller than the second, when compressed against the 

 ventral surface, scarcely reaching to the bases of the latter. The sec- 

 ond pair, which arises from the posterior thoracic lobes, when com- 

 pressed in the same manner, do not reach much, if any, beyond the 

 middle of the first abdominal segment. In distended specimens the 

 thoracic appendages project ventrally at an angle of more than 45 de- 

 grees, but in distorted ones they may lie more or less flat against the 

 surface, the posterior pair often reaching to or slightly overlapping the 

 second abdominal segment. 



The ovigerous tubes are nearly as long as the body, sometimes longer, 

 large, and slightly tapering; rounded at the ends. 



By contraction, or by distortion in alcohol, this species assumes verj^ 

 odd and irregular shapes, which it is impossible to describe in detail; 

 but it is always readily distinguished from the other species of the genus 



