ECHINOIDEA. II. 



Phormosoma placenta W. Th. In the Echinoidea d. deutschen Tiefsee-Expedition (p. 12628) 

 Doderlein points out that the specimens of Phormosoma placenta from the Davis Strait as well as 

 that figured in the Blake-Echinoidea differ from the specimens from the European side of the 

 Atlantic, in having fewer abactinal plates in the ambulacra and interambulacra ; in the European form, 

 the typical placenta, there are 10 n interambulacral and 14 16 ambulacral plates in each series, in 

 the specimens from the Davis Strait there are only 78 interambulacral and 910 ambulacral plates. 

 The latter form is thus maintained as a distinct species, Ph. sigsbei A. Ag., though it is suggested that 

 on examination of a richer material it will, together with the species from the Indian Ocean: Ph. 

 adenicum, indicum and bursarium, prove to be only a variety of Ph. placenta. This suggestion is no 

 doubt correct, as regards Ph. sigsbei at least. Several specimens before me from the Faroe Channel 

 ( Michael Sars 1902) as well as some from the Thor are quite intermediate as regards the number 

 of abactinal plates, so that it is impossible to decide thereby to which form they should be referred. 



I give here some instances. The tridentate pedicellaria; in these 

 Diameter Number of abactinal P lates specimens, however, are of the slender form, the character derived 



Interambulacra Ambulacra 



8omm s 12 from the form of these pedicellarias, viz. narrow in the typical pla- 



centa, broad in sigsbei (comp. PI. XII. Figs. 2 3 and 7 of the Part I) 

 88 89 13 thus apparently being more constant. To distinguish Ph. Sigsbei 



90 8 9 IT 12 



__ 8 J2 as a separate species from placenta seems then scarcely justified, 



but it may be correct to maintain it as a variety besides the typical 



form of Ph. placenta, the latter belonging to the European side of the Atlantic, the var. sigsbei to the 

 American side, from the Davis Strait to the West Indies. 



Mr. R. T.Jackson has called my attention to the fact that in the figure of a young Phormo- 

 soma placenta given in the Siam-Echinoidea I. (p. 54) the teeth are represented as situated in the 

 ambulacra. I take the occasion here to correct the error, which I can scarcely account for. The teeth 

 are distinctly interambulacral also in the smallest specimens, as might, of course, be expected. 



Hypsiechinus coronatus Mrtsn. Mr. R. T. Jackson likewise suggests to me that the plate 

 outside the buccal plates, between the terminal plates, shown in PL VII. Fig. 6 of Part I ought not to 

 be interpreted as the basal (genital) plate as I have done (p. 89), but as the first interambulacral plate. 

 Mr. Jackson is right in this suggestion. I have examined the specimen figured there and find that 

 the genital plates are also present, and easily discernible, when examining the specimen from the 

 abactinal side, so there is no excuse for the error. 



Echinus gracilis. In the Echinoderms of Bally nakill and Bofin Harbours, Co. Galway and of 

 the Deep water off the West Coast of Ireland* by Stanley W. Kemp (Ann. Rep. Fish., Ireland. 

 1902 3. Pt II. App. VI. 1905) is named (p. 199) Echinus gracilis (Diib. and Kor.). As Dub en and 

 K o r e n have described no Echinus gracilis and the Ech. gracilis A. Ag. was hitherto known only from 

 the American side of the Atlantic, I wrote to Mr. Stanley Kemp about the matter, and he informed 

 me that it was an error for Ech. elegans Diib. Kor. I take the occasion to correct the error here to 

 prevent introducing in literature Ech. gracilis as occurring on the' European side of the Atlantic. 



Echinus csculentus L,. The variety of this species mentioned in Part I. p. 162, and further 

 mentioned by Appellof (Havbundens Dyreliv. Norges Fiskerier. I. Norsk Havfiske, i. Del. Havforsk- 



