69 



Radula: not investigated. 



Colour: as the foregoing species. 



Length: the largest specimen measured 3 mm. 



Remark: The specimen of Stat. 141 shows round its aboral pole a thickened white 

 margin, indicating a posterior ciliated ring. The fringes on the radiating crests of the posterior 

 gill are not formed yet. As the buccal appendages of this specimen exhibit the same number of 

 suckers as those of the two other specimens, I think this larval form may be identical with them. 



Perhaps two other larvae from Stat. 165 may be assigned to this species. The 

 length is 2 mm. The foot is smaller, more pointed. Gills are wanting, but some traces of two 

 ciliated rings are visible. First I regarded these small specimens as some Spongiobranchaea, 

 but this view is contrary to the form of the acetabuliferous appendages (as in Pn. pygiiiaeum), 

 and also to the rather strong development of the hook-sacs which contain many long, slender 

 hooks. At any rate these specimens (fig. 123) are larvae of a Pneuinonodcruia . 



In the literature two species have been described as belonging to Pneiciiioiwderi/ia ; but 

 these descriptions are very insufficient. We ma)-, however, draw attention to these forms, as 

 they were obtained in the harbour of Amboina. 



One of them, "■ Pneumodermon r^iber' Quoy et Gaimard ') may be a Clionopsis as Boas 

 thought^); but the presence of a lateral gill speaks against this opinion. As "variete" of this 

 species Ouoy and Gaimard described ^) some forms which are very likely Pneuinonodcrina^ but 

 about which nothing can be decided. 



'^Pneumodermon pellucidtis" of the same zoologists'*) seems to be a Clionopsis ")\ but 

 here too a lateral gill is figured. Its systematic position must therefore remain uncertain. 



It is very unfortunate that the type specimens of these interesting forms are lost, so 

 that any discussion about them is nothing but conjecture. 



Anatomical Remarks. 



The anatomy of the Pneumonodermatidae has been ampl)- studied by Pelseneer ^) whose, 

 very accurate researches will be the base of our knowledge with regard to the anatomj- of 

 the whole family, and, indeed, of all the Gymnosomata. 



I had only little material for examination, viz. some '~,\}iic\m&n?, oi Pnenmonoderma mcditer- 

 ranenm from Naples (kindly presented by Dr. Nierstrasz), of Pn. pcroni (Leyden Museum), 

 of Pn. violaceum (Amsterdam Museum), and of Spongiobranchaea ansfralis (Utrecht Zoological 

 Museum). As only the representatives of the first named species were sufficiently preserved, I 

 have studied those particularly. 



It seems quite unnecessary to me to enlarge upon the researches of previous authors 



1) Voyage de r.\strolabc, vol. II, p. 389, pi. 20, figs. 19 — 20. 



2) Spolia Atlantica. p. 171. 



3) Op s. cit., p. 390, pi. 20, figs. 21—24. 



4) Op s. cit., p. 390, pi. 28, fig. 25. 



5) This opinion has been expressed by Bo.\s, Spolia atlantica p. 171. 



6) Challenger Rep. LXVl, p. 38—45. 



