REPORT ON THE DIATOMACE/E. 169 



Ethrnodiscus obovatus, n. sp. (Plate XVII. fig. 5.) 



Forma minima late obovata, nodulo grandiuseulo umbilicali, raris puuetulis circum 

 sparsis, et margine distinctioribus granulis signato, iustructa. Ad mare Arafura. 



This type has some resemblance to the last, but its form is oval, and it exhibits a 

 slight deviation in the regularity of its outbne at one point. It possesses a large granule 

 in its centre and its margin is also marked by a number of somewhat smaller though 

 distinct granules. Between the marginal corona and the centre of the disc a small 

 number of irregularly disposed rounded points occur. . 



Ethmodiscus perichantinos, n. sp. (Plate XXII. fig. 3.) 



Forma suborbicularis, vix conspicue striolata, irregulari punctulorum agmine umbili- 

 cali, raris punctulis ad marginem et varise magnitudinis sparsa, et punctulorum eorona 

 spiuulosa cincta. In mari Arafura. 



This species, of which several specimens were obtained in the Arafura Sea, has a 

 rounded and irregular outbne, and exhibits a radiating striation which is very difficult to 

 recognise. There is an irregular group of small granules at its centre, its margin is strewn 

 with thiuly scattered puncta, and its border is granulated and thorny. 



The specific name of this form is derived from the condition of its border. 



Ethmodiscus diadema, n. sp. (Plate XVIII. fig. 1.) 



Forma mediocris, convexiuscula, radianter striolata, margine variorum processuum 

 corona insignita. In Antarctico, ad meridiem insulse Heard. 



This type, which was found in the icy Antarctic Sea to the south of Heard Island, 

 possesses a disciform convex frustule. It has conspicuous radiating striae and its margin 

 is adorned by several (20) large granules or more salient points, which are disposed at 

 somewhat irregular intervals. 



The specific name has reference to the presence of salient marginal puncta. 



The examination of several fragments of connecting zones belonging to the extremely 

 large Diatoms already alluded to, revealed the existence of several species, of which the 

 following are noteworthy : — 



Ethmodiscus gigas, n. sp. (Plate XIV. fig. 5.) 



Forma rotunda, maxima ; valvis convexis insequalibus quarum una cum area umbili- 

 cali (?) ; lineolis radiantibus (?) ; cingulo cylindrico punctulato. Diametrum = 1633 //. In 

 Atlantico, ad insulas Capo Verde. 



This is a very large form provided with valves which are unequal, one being more 

 convex than the other. It possesses an umbilical areola which may be of varying size, 



(bot. chall. exp. — part iv. — 1886.; D 22 



