1908] Kofoid. — Exuviation and Autotomy inCeratium. 357 



stance, is to be found in tiiiiires 11 and 12. In a collection of 

 plankton of seniitropical contents taken off San Diego in July, 

 1905, there occurred a Ceratiinn arcuatum (?) which exhibited 

 unequivocal evidence of recent exuviation. As will be seen in the 

 figures the specimen is possibly the anterior schizont of a recent 

 division. The posterior segment of the theca, separated from 



ap. p 



Fig. ii.—Ventral view of Ceyaiium arcuatum (?) in process of exuvia- 

 tion. X 375. 



Fig. 12.— Dorsal view of the same. X 375. After sketclies by Miss 

 Marie Griffiths. 



Specific identification is uncertain in the absence of the complete ant- 

 apical horns. Precingulars 1" and ^" and post-cingulars 1'" and ^"' and 

 adjacent girdle are senile plates. The others are all of recent formation. 



the anterior by a dotted line in the figures, was very thin-walled 

 and bore all the signs of recent formation. The anterior segment 

 on the other hand had certain plates with strongly marked senile 

 characters while its other plates were of very recent origin, being 

 in fact visible only as exceedingly thin films. The senile plates, 

 four in number, including precingulars 1" and 2" and postcing- 

 ulars 1'" and 2'", together with those segments of the girdle 

 plates which go to the anterior schizont in division, were ex- 

 ceedingly thick-walled, with a rugose surface deeply pitted by 



