1903.] FROM EAST AFRICA AND ZANZIBAR. 355 



Trippa Bergh. 



12. „ areolata {K. kH.). 



13. ,, monsoni, sp. n. 



Fracassa Bergh. 



14. ,, tuberculosa. 



Halgerda Bergh. 



15. ,, willeyi, sp. n. (From the Loyalty Island.s.) 



16. „ loasinensis, sp. n. 



Kentrodoris Bergh. 



17. ,, rubescens Bergh. 



Platydoris Bergh. 



18. ,, eurychlamys Bergh. 



19. ,, scabra (Cuvier). 



20. „ formosa % (A. & H.). 



21. „ e^^to«t ? (A. & H.). 



22. ,, pulchra, sp. n. 



23. ,, incerta, sp. n. 



24. ,, papillata, sp. n. 



Sclerodoris Eliot, gen. n. 



25. ,, osseosa (Kelaart). 



26. ,, tuberculata, sp. n. 



27. ,, minor, sp. n. 



28. ,, rubra, sp. n. 



29. „ coriacea, sp. n. 



Asteronotus Ehrenberg. 



30. „ hemprichi Ehrenberg. 



The Cryptobranchiate Dorids are distinguished by having 

 branchiae which are completely retractile into a permanent pocket. 

 The rhinophores also are retractile into permanent pockets and 

 are perfoHate. A radula is always present. In number of 

 species they form one of the richest groups of the Nudibranchiata, 

 but they show less variety of form than the Dorididas Phanero- 

 branchiatae, and it is not easy to find good generic characteristics. 

 The most distinctly marked group is that consisting of the large 

 genus Chromodoris (with more than 100 species) and some allied 

 genera such as Casella and Ceratosovia. These possess a charac- 

 teristic shape, lip-plates, a radula with differentiated teeth, and 

 simply pinnate branchiae. Well characterised genera are also 

 found in the Miamiradse {Miamira, Orodoris, Sphoerodoris) and 

 the Cadlinidse {Oadlina, Tyritma). There remain the five sub- 

 families mentioned above, which agree in being usually flat and 

 oblong in form and in having a radula without a central tooth, 

 consisting of numerous laterals which are generally hamate and 

 uniform, though often smaller near the rhachis and degraded or 

 denticulate at the outer end of each row. 



Anyone who describes new forms of these Dorids, however 

 much he may disclaim any such ambitious task as a revision of 



23* 



[3] 



