64 THE VOYAGE OF H.M.S. CHALLENGER 



This exceedingly elegant frustule possesses a subrotund form. It is slightly folded, 

 and has a series of long costules, which are, however, not quite half the length of the radius, 

 placed regularly round the periphery. These originate from a granulated circular line 

 which circumscribes a central smooth oval area. The costules are divided from one another 

 throughout half of their length by a simple line ; in their outer half they become constricted 

 and are rounded at their extremities, being at the same time separated by finely granu- 

 lated areas, ornamented by minute quadrately disposed points. The extreme edge 

 of the valve bears a circlet of minute granules, and the margin is provided with short 

 spines. 



Campylodiscus humilis, n. sp. (Plate XL fig. 8.) 



Forma parva, flexuosa, ephippiformis ; costulis vel canaliculis ab area sublineari 

 radiantibus ; costse utrinque a linea centrali profunde inflexa. Ad insulas Philippinas. 



This small form bears a great affinity to Campylodiscus zebuanus, from which, 

 apart from a difference in size, it may be distinguished chiefly by the two following cir- 

 cumstances : (1.) It is far more elliptical than the latter, and (2.) the line of inflexion, 

 instead of being but slight, is well-marked. Although it is not possible to determine 

 the true specific value of these differences, the form now in question has been provisionally 

 regarded as a distinct species. 



Campylodiscus philippinarum, n. sp. (Plate XL fig. 9.) 



Mediocris, ephippiformis ; crebris costulis (centum et amplius) in tres ordines 

 inasquales irregulariter divisis, a quibus area subrotunda circumscribitur, medio punctulis 

 raris quadratim dispositis vix perspicuis signata. Ad mare Philippinarum. 



This frustule, which was collected in the Philippine Sea, possesses a disc of moderate 

 size, which, by the flexion of two of its axes, appears somewhat quadrate in outline. It 

 has a corona of numerous radiating costules, which are separated by an undulating line into 

 two rows of unequal size, while the inner and larger is surmounted by a third row of short 

 cellules. The large central area is ornamented by a number of minute scattered granules, 

 which are arranged in a quadrate manner. 



Campylodiscus orbicularis, n. sp. (Plate XVI. fig. 10.) 



Valvis subrotundis vix flexuosis, area elliptica lsevi lineolarum serie cincta ; costulae 

 subradiantes (42) ad utrumque polum divisse. In mari Japonico. 



At first this form seems to be a variety of Campylodiscus lepidus (Plate XL fig. 7), as 

 both possess approximately radiating costules or canaliculi, and in the centre of both there 

 is an oval hyaline area circumscribed by a series of small lines. The structure of the margin, 

 however, is completely different in the two types. In the former the border is coarsely 



