916 Transactions of the Society. 



remarks on Ilyahdiscus maximns {CydoteJla maxima Kiitz.). Ac- 

 cording to Prof. H. L. Smith, wLo possesses original specimens, it is 

 identical with the latter, an opinion which Grunow is unable to 

 adopt. 



E. commutatus Grev. (Moll. Cat., 1883, fide Habirsh. Cat. Diat 

 § Enj)odiscus) has been named by some Coscinodiscus concinnus var. 

 commutata ; it may be united with the older E, jonesianns (Grev. 

 Trans. Mic. Soc. Lond., 1862, p. 22, pi. ii. fig. 3) which is a var. of 

 Coscinodiscus concinnus. 



E. Wei ssjlor/ ii Grnn. (Typ. Syn. Diat. r)elg., No. 11) has been 

 justly associated to Eupodiscus with hesitation by Van Heurck who, 

 in the explanation of his slide, has provisionally united it to Micro- 

 podiscus Grun. To this genus, modified from its original conception, 

 it may be united. 



E. piunctatns Bail, is an ]\IS. name found in Bailey's collec- 

 tion, but remains a nomen midum (Habirsh. Cat. Diat, 2nd ed., 

 § Eupodiscus). 



E. Bebii Grove & Sturt (Grun. in Bot. Ceutralbl., Bd. xxxiv. 

 Nos. 15-16, p. 38) is Lampriscus (?) Dehii Grove & Sturt (Journ. 

 Quek. Mic. Cl., 1887, p. 158, pi. xi. fig. 27). To neither of these 

 genera is this valve readily assignable, and I regard it as the type of 

 a new genus Isodiscus. 



The transition to Biddidphia from Eupodiscus is found in the 

 Oamaru Biddulphia lata Grove & Sturt (Journ. Quek. JMic. CL, 1887, 

 p. 135, pi. xiv, fig. 53). 



AiiTiFiciAL Key. 



1 . Slarkings delicate 2 



„ well defined and more evident 3 



2. Processes 4. Markings punctate, irregular at centre, elsewhere 



in oonccutric bands imnctnlatus. 



IMarkings not in concentric bands 4 



4. Processes 1 or 2. Markings 5 to 6, decreasing gradually out- 



wards to 8 iu O'Ol mm.; rows curved, subfas- 



ciculate parvulus. 



„ 3, circuliir. Markings unequal, 2i to 3 in O'Ol mm., 

 without order, an imlistinct baud roiind each 

 process trioculatus. 



„ 4, inserted at one-fourth of radius from circumfer- 

 ence, prominent on their outer edge. Markings 

 5 iu 0" 01 mm., subequal, without order .. .. minutus. 



3. Apiculate 5 



Non-apiculate 6 



5. Apiculi 3, equidistant from the 3 processes. Markings 6 to 8 



in 0-01 mm., rows radial, a distinct band round 



each process californicug. 



„ 2, equidistant from the 2 processes. Markings largest 

 at centre, decreasing rapidly outwards from 3 to 6 

 in O'Ol mm., rows oblique, curved, decussating .. decrescens. 



„ numerous, forming a distinct circlet close to border. 

 Markings subeqnal, 4 in 01 mm. Processes 2, 

 large, oval, with long axis radial simplex. 



,, evident, forming a circlet close to border. Markings 

 equal, in straight, oblique, decussating rows. Pro- 

 cesses 3, elliptical, with major axis at right angles 

 to radius nebulosus. 



