6 F. A. SMITT, 



with each other. Now, in the collections from Florida, of the subgenus Idmonea, we find 

 at least three, in their typical state, yery easily distinguished species. But even of these, 

 the two very much approach each other in their variations; and the third is distin- 

 guished from the others by a characteristic, which is, by some authors, regarded as 

 geuerical. 



Idmonea atlantica (Pl. II, tigs. 7, 8), 



the best known species of this group, with its great geographical range, is here repre- 

 sented by some colonies of that slender form, that we have found even in the most 

 northern deep seas as well as in the great depths (200 — 300 fathoms) at the Azores. 

 Pourtales found it at from 60 to 270 fathoms, the latter off Havana, whence he has 

 described it in the most slender form under the name of Idmonea flexuosa. And, in 

 truth, if this (see the figures 7 and 8) should be a common and constant form in that 

 locality, it will be well to retain that name for it, as a local variety; but, otherwise, 

 it represents nothing but the first stages of the growth of the common form, more 

 than usually prolonged. Now, with all the variations of this kind, that I have seen on 

 the Scandinavian Idm. atlantica, I have no hesitation in combining these two forms as 

 the same species, especially as Pourtales has brought up the typical form from a depth of 

 60 fathoms. The museum at Stockholm has also received this from Gnlf S:t Vincent 

 (Austr.) through the Godeffroy-mnseum. 



Higher up in the sea, at 15 fathoms, Pourtales has taken another form in this 

 group (see figures 9 and 10) with the structure of /. atlantica, but with the zocecia 

 almost double as great, about 3 m.ra. broad in the raised portions. In this resj)ect, it 

 resembles the Idm. serpens; and as in this group of Idmonea, the size of the zocecia, 

 in the corresponding stages of growth, gives the most appliable characteristic, we must 

 regard it as coming nearest to the latter form. This usually, when erected, presents 

 a greater number (4 — 5) of zocecia in the transverse rows, even in its lowest parts, and 

 I have never seen it growing so narrow as this Floridan specimen. In the Quart. 

 Journ. Micr. Se, vol. VI, pl. XVIII, fig. 5, Busk has given a figure of a Madeiran 

 Idmonea atlantica with only two zocecia in each row; and in the text he says, that it 

 is, »comparatively», of a »greater size and of more robust habit» than the northern, eu- 

 ropean form. This will, perhaps, turn out to be the same; and if it should be found 

 as a constant southern variety, it would be worthy a separate name. Now, with a 

 single specimen, and this, without doubt, not full grown, it is impossible to judge in 

 this question; but so much we can say with certainty, that, in regard to the form, it 

 holds the same position to the Idm. serpens, as Pourtales' Idm. flexuosa shows itself 

 to do, when compared with Idm. atlantica. The typical Idmonea serpens I have not 

 found in Pourtales' collections. 



Nearer to Idm. atlantica, as to the size of the zocecia, although differing more 

 in habit, comes the 



Crisina Hochstetteriana (Pl. II, tigs. 11 — 18), 



first described by Stoliczka as a tertiary fossil found in the Orakei-bay, Auckland, 



