TESCH— PTEROPODA AND HRTEROPODA 189 



Plate 13. 



Fig. 1. Pterosoma planum, seen from above, x 12. a. anus; at. atrium of the heart; e. eye; k. kidney; 

 sg. salivary gland ; t. tentacle ; v. ventricle of the heart ; vn. visceral nucleus. 



Fig. 2. The same, seen from the right side, x 12. 



Fig. 3. Visceral nucleus of the same, seen from the left, x 24. at. atrium of the heart ; g. gills ; 

 int. intestine ; mr. thickened margin of mantle ; n, visceral nucleus ; os. osphradium. 



Fig. 4. Fin and its neighbourhood, from the right, x 30. f. fin ; p. penis ; s. sucker. 



Figs. 5, 5 a. Transverse row (31st) of radula of same, x 320. Fig. 5 central plate ; fig. 5 a inter- 

 mediate and lateral plates, cp. central plate ; cp'. central plate of 6th row ; ip. intermediate plate ; 

 1st Ip. 2nd Ip. first and second lateral plate. 



Plate 14. 

 Fig. 1- Pterotrachea scutata, from the left, x 3. 



o 



Fig. 2. Head and proximal part of trunk of same, another specimen, from above, x 3^. 



Fig. 3. Mouth of same, from within, cut open ventrally, and spread out to show the peribuccal 



teeth, x 20. dg. dorsal group of peribuccal teeth ; Ig. lateral group ; vg. ventral group. 

 Fig. 4. Pterotrachea (Euryops) mutabilis, from the right side. x 4. at. atrium of the heart 



k. kidney ; ok. opening kidney to the exterior ; v. ventricle of the heart. 



