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 issue 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 m 
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, mhabit 
the coralline zone. 
Cuemnitzia 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 subrotund congeries of 30-40 
flake-white points close behind the eyes. The spire of the 
operculum is more complete than im any other Chemnitzia 
T am acquainted with. 
