128 PROCEEDINGS OF THE ACADEMY OP [1879. 



Tritonia tetraquetra (Pallas). 



13. aa, the foot; b, the corner of the frontal veil ; c, margin of the . 



genital opening; d, penis with the opening of the mucus 

 gland under its root. 



14. A branchial leaf or plume. 



15. a, the anal papilla; b, the renal pore. 



16. Part of the cutting edge of the processus masticator ius, ^. 



Plate IV. 



Dendronotus arborescens (0. F. Miiller). 



1. Masticating edge of the jaw, posterior end,* -. 



2. Elements of the prehensile collar,* ^|o. 



3. Point of the penis ; a, orifice,* ^. 



4. Penis;* d, vas deferens; b, point of the organ, ^. 



Tritonia tetraquetra (Pallas). 



5. Part of the cuticle of the frontal veil. 



6. The buccal ganglia, with b the right gastroesophageal 



ganglion,* ^. 



7. The mandibles from in front ;* a, articulation ; b, j^ocessus 



masticator iu s. 



8. 8. Teeth from the middle of the radula, parts of three rows, 



seen obliquely from above ;* aa, median teeth ; bbb, first 

 laterals from the left side ; cc, same of the right side ; dd, 

 second laterals of the left side, ^. 



9. Lateral teeth from the middle of a row,* ^p. 



10. Outer teeth (6-9) of two rows;* aa, the outermost; b, fold 



of the cuticula, ^p. 



11. Outer teeth (5-4) of two rows; a and b as above, ^. ' 



12, 12. Doubled (monstrous) teeth of two rows,* ~. 



Akiodoris hdescens, Bergh. 



13, 13. Spicula of the skin.* 



Plate V. 

 Tritonia tetraquetra (Pallas). 

 1. Pvhachis or median part of the radula, with part of three rows 

 of teeth ;* aa, rhachidian teeth ; bb, first lateral teeth ; cc, 

 second laterals, ^y 2 . 



