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



surfaces do not show the well-defined points which are so manifest in Lauderia 

 anmdata, Cleve, and Lauderia elongata, described above ; on the contrary, a crown of 

 marginal granules is alone represented. If then this organism be accepted as a Lauderia 

 the definition of the genus must be extended to embrace both these conditions. 



Lauderia (?) moseleyana, n. sp. (Plate XXIV. fig. 9.) 



Forma cylindrica, annulata, parum longior quam latior ; liuea suturali excentrica ; 

 margine granulato. In mari Arafura. 



This cylindrical Diatom from the Sea of Arafura is annulated and terminated by fiat 

 surfaces. The rings, however, though still of considerable diameter, are markedly narrower 

 than in the preceding types. The individual frustules of a series are terminated at each 

 extremity by a distinctly granulated line, and each at the same time presents a well-marked 

 transverse line of suture which crosses the frustule nearer one end than the other. These 

 lines are approximately at the same distance from the granulated terminal bands on both 

 sides of each granulated area, so that two adjoining wider and two adjoining narrower 

 zones succeed each other regularly. 



The specific name has been given in honour of Professor Moseley of Oxford, who 

 accompanied the Challenger Expedition as one of the Naturalists. 



Rutilaria, Grev. 



In 1863 Greville 1 established this genus for some rare and singular fossil organisms 

 discovered in the deposits of Monterey and Barbados. Having only seen the valve of 

 the frustule, the original definition was not, as might be expected, exact ; but, after the 

 discovery of other frustules adhering to one another, he amended this in 1866 in the 

 following manner : 2 — "Frustules very compressed, cohering into a short filament; valves 

 slightly elevated at the angles, with a central glistening nodule prolonged into two short 

 linear, obtuse processes ; the margin pectinate-ciliate." 



The affinity of this genus with that of Biddulphia, which has also been recognised by 

 Greville, presents no difficulty after a simple examination of its valval side, while the 

 presence of a large central convolute nodule prevents it from being confounded with the 

 genus Nitzschia. On the valval side of Rutilaria there may also be seen a well-defined 

 elevation at each of the extremities. In Biddulphia, on the other hand, terminal processes 

 or cornua occur, while generally the centre is convex and salient, and the adjoining frustules 

 become united to one another by means of two long spines or setae. 



1 Quart. Journ. Micr. Sci., n. s., vol. iii. p. 227. The original definition ran as follows: "Frustules free, 

 elongated, compressed, with a convolute or nodulose central nodule (no median line or terminal nodule), and 

 minute radiate or decussato-punctate structure. Valve (linear, keeled?) with a longitudinal row of puncta." 



2 Trans. Micr. Soc. Lond., n. s., vol. xiv. p. 124. 



