116 THE VOYAGE OF H.M.S. CHALLENGER. 



argus, A.S., in fig. 12 ; and finally, Stictodiscus morsianus, A. S., in figs. 19 and 20. The 

 forms marked figs. 21, 22, and 23 are given as doubtful, while those of figs. 13, 14, and 15 

 are interpreted as internal valves 1 of Stictodiscus — a determination which seems to rest on 

 no other foundation than the presence of evanescent folds towards the centre, there being 

 no trace of any such reticulate arrangement as occurs in Stictodiscus. It would seem 

 rather that such discs belong to the genus Cyclotella, of which they would constitute 

 a new species. 



On plate lxxv. fig. 1, Schmidt has represented a superb polygonal Stictodiscus under the 

 name of Triceratium multiplex, Janisch (?). It possesses a central corona, and the almost 

 regular short lines of granules form a belt at the circumference, while the middle of the 

 surface is covered with sparsely disposed granules of a similar kind. The very large valve, 

 which has arrived at its complete development, scarcely preserves traces of the folded 

 condition of its surface, but I do not hesitate to designate it Stictodiscus multiplex. 



In fig. 2 of the same plate the organism represented as Triceratium jercmianum, A. S., 

 is another subquadrate Stictodiscus with subradiating folds which alternate with granular 

 lines, that subsequently become rare and are irregularly scattered in the middle. Many 

 lines of small granules occur at the angles, and these point, as in other allied forms, to 

 its progressive development. This form should accordingly be designated Stictodiscus 

 jeremianus. 



At figs. 6 and 7 Schmidt also shows two different forms of Triceratium, established 

 by Greville, which, as already said, must be named Stictodiscus eulensteinii ; while the 

 Triceratium karri sonianum, Grev., shown at Plate lxxv. figs. 14 to 16 should be 

 designated Stictodiscus harrisonianus. 



On plate lxvi. of this Atlas several other forms which have been named Triceratium 

 appear to me to be true Stictodisci, although the essential characters of the latter genus 

 are in these less evident than in the above-mentioned cases. 



In considering the new types belonging to the genus Stictodiscus which have been 

 brought home by the Challenger I shall first refer to the discoidal forms, and then pass 

 on to those which are polygonal. 



I. Discoidal Forms of Stictodiscus. 

 Stictodiscus anceps, n. sp. (Plate I. fig. 5.) 



Granulis raris in lineas subregulares radiantes distributis; centrum punctulorum corona 

 distinctum. Ad oras Japonicas. 



1 "Nach meiner festen Ueberzeugung innere Schalen v. Stictodiscus. Solche innere Schalen, welche nament- 

 lich bei Asteromphalus und Asterolampra vielfach vorkommen und irrthumlich als besondere Arten benarmt sind, 

 sind leicbt daran zu erkennen, dass sie theils einen Stich ins Yiolette haben theils der feineren Sculptur ermangeln, 

 uberhaupt roher gestaltet sind. Grunow bestimmt die vorliegendon Figuren als Schalen von Metosira clavigera, 

 Grunow." 



