ADDENDA ET CORRIGENDA. 



Porocidaris purpiirata W. Th. Several specimens were taken by the Thor at 62 57' L,at N. 

 19 58' Long. W. 957 M. (off South Iceland) in 1903 and at 49 25' I/at N. 12 20' Long. W. 1270 n8oM. 

 (off Southwest Ireland) in 1905. The Porocidaris elegans mentioned by Koehler in Echinodermes 

 du Caudan (226. p. 89) is, as Professor Koehler kindly informs me, P. purpurata. 



In Part I. p. 173 I have established a var. Talismani of this species, characterised by the 

 upper primary radicles having the neck swollen in a fusiform manner and of a fine violet colour. The 

 specimens taken by the Ingolf have not the neck of the spines thus swollen, so that the specimens 

 from the Talisman*, which show that feature exceedingly developed must necessarily appear to me 

 at least a distinct variety. The additional material from the Thor, however, shows that this variety 

 cannot be upheld. Among these specimens all transitions may be found from such specimens with 

 the neck of the spines not at all swollen to such with the neck of most of the upper spines consider- 

 ably swollen, and this swollen part of the spines is of a beautiful violet colour, which sometimes 

 continues almost to the point of the spines. The specimens upon which the var. Talismani was 

 established thus cannot be regarded as more than extraordinary beautiful specimens of P. purpurata. 

 For the rest the swelling of the spines has been sufficiently represented by Wyv. Thomson 

 (Porcupine-Echinoidea. PI. I/XL Figs. 1,4, 6) though he does not mention this peculiar feature in the 

 text. It may be remarked that the neck is much longer in the upper spines than in those at the 

 ambitus and on the actinal side. 



Tretocidaris annulata Mrtsn. The examination of some specimens of Tr. Bartle.tti (A. Ag.) in 

 the U. S. National Museum has convinced me that Tr. annulata is only a synonym of the latter 

 species. The description of this species given in the Blake-Echinoidea is so very insufficient that 

 it is scarcely possible to recognise the species thereby, and even the Fig. 16. PI. II of the Blake-Ech. 

 gives a quite wrong representation of the ambulacra. In the description (Blake-Echinoidea. p. 10) it 

 is said: the poriferous zone is somewhat flexuous, the furrows more distant, and the median ambu- 

 lacral granulation finer, than in the other West India species of the genus, and the figure shows the 

 ambulacra closely covered by tubercles, three on each plate, without any naked space in the middle. 

 But the ambulacra of this species are really as I have described for Tr. annulata (Part I. p. 17), each 

 plate bearing only one small tubercle at the lower edge, inside of the primary tubercle, leaving a 

 broad naked space along the median line. Only in the largest specimen (68 mm ) is there in some of 

 the median ambulacra! plates a third small tubercle inside the second tubercle, but still the naked 



The Ingolf-Expedition. IV. 2. 22 



