294 



GRIFFIN. 



Fig. 2. — A cross section passing 

 through the mouth, the adoral 

 membranelliB. a. ~., and the 

 suboral membranellae, s. o. 



mouth, the sub- 

 oral membranell<e, 

 the pharynx and 

 pharyngeal mem- 

 branellEe, and the 

 adoral zone. 



Mouth and phanjii.v. — The mouth i.s situated iipon the vertical median 



wall of the peristome. 

 The curving piosterior side 

 of the peristome forms its 

 posterior and part of its 

 dorsal margin. 



The outline of the 

 mouth, instead of heing 

 regularly round or oval, is 

 quite irregular, being about 

 twice as wide along the 

 ventral edge as along the 

 dorsal. The ventral ex- 

 -oss sec- tension of the mouth and 

 pas sing jjharynx accommodates a 

 group of membranellfB to 

 which I have applied the 

 name suboral. (Plate I, 

 figure 1 ; Plate III, figure 

 5; text figures 2 and 3.) 

 The bases of the suboral membranellse lie in a definite oval area, possibly 

 a region where the pellicle is thinned. By examining living specimens 

 it was impossible to determine whether the suboral 

 membranellte were upon the ventral lip of the 

 mouth, or upon the projection of the anterodorsal 

 wall. The latter seemed to be the case. It was 

 only when sections had been made that the exact 

 j)osition of the suboral membranellffi was demon- 

 strated. Just posterior to the suboral membra- 

 nelte is a small elevation of the floor of the 

 pliarjTix. (Text figm-es 3 and 6.) 



The pharynx passes to the right and forward, 

 its j)Osterior outline being a continuation of the 

 regular curve of the outer wall of the peristome. 

 The phaiyns narrows considerably Just inside the 

 mouth, after which the anterior wall approaches 

 the posterior very gi-adually. The inner end of 

 the pharynx is blunt and comparatively wide. The 

 anteroventral angle of the pharynx forms a deep 

 groove which extends from the corresponding angle 

 of the mouth to past the middle of the pharynx. 

 (Plate III, figure 5; text figure 4.) 



The zone of adoral membranellse continues into 

 the i^harynx without a break, altliough with a 

 gradual reduction in the length and breadth of 



Fig. 4. — A longitudinal 

 section, showing the 

 anteroventral groove of 

 the pharynx. 



