522 APPENDIX. 



CHEMNITZIA PLICATA. (P. 418.) 



Rostrum long, presenting at its termination a flat disk, 

 which exhibits at times the very opposite phases of subcir- 

 cular and subquadrangular form; it issues from under the 

 coalition of the tentacular membranes, and is attached to the 

 foot by a bridle. The tentacula terminate in rounded sub- 

 lanceolate points which are very slightly marked with the cha- 

 racteristic apical inflations of the tribe. The half of the rostrum 

 nearest the eyes is thick and wrinkled when not much pro- 

 truded, and at its upper basal portion, just below the eyes, 

 the proboscidal fissure is apparent. This is one of the species 

 from which I have seen the issiie of the retractile proboscis. 

 The foot has very small auricles ; on the march it becomes 

 considerably elongated and reflexed upwards, but still retains 

 an obtuse point. 



The subcylindrical variety of C. unidentata often passes in 

 collections for this species, which is a decided littoral animal. 

 The slender C. acuta has also been erroneously considered 

 the C. plicata \ but this last, and the C. unidentata, inhabit 

 the coralline zone. 



CHEMNITZIA ACUTA. (P. 420.) 



This species shows in a marked manner that the rostrum 

 (the mentum of authors) is really the head of the animal. 

 This organ is channelled from its termination to its base, at 

 which point, between and just under the eyes, the fissure is 

 evident, from which I have more than once seen the evolution 

 of a long proboscis. The anteal portion of the rostrum is 

 without any sort of orifice, but it is probably a tentacular aid, 

 and also one of progression. Every one that examines this 

 organ will unquestionably pronounce it the capitular part of 

 the animal, and will discard the term mentum. 



In many specimens there is a subrotuud congeries of 30-40 

 flake- white points close behind the eyes. The spire of the 

 operculum is more complete than in any other Chemnitzia 

 I am acquainted with. 



