OF THE COSCINODISCEiE. 



835 



Dcedalm, 92; A. CalUmachus, 93; A. 

 Phidias, 94 ; A. Praxiteles, 95 ; A. Pyr- 

 goteles, 96 ; A. Apelles, 97 ; A. Zeiixis, 

 98; A. Orjyheus, 99 ; A. Apollo, 100; 

 A. Adamas, 101 ; A. Achates, 102 ; A. 

 Amethi/stus, 103 ; A. Astrolites, 104 ; 

 A. Benjllus, 105 ; A. Carhunculus, 106 ; 

 A. Chrysolithus, 107 ; A. Hyacinthus, 

 108 ; A. laspis, 109 ; A. lasponyx, 110 ; 

 J[. Leucochrysus, 111 ; ^. Omphus, 112 ; 

 ^. 0/2?/j7, li3; A. Opalus, 114; ^. ^Sa- 

 phirus, 115; ^. Sarda, 116; ^. Sardonyx, 

 117; ^. Smaragdus, 118; ^4. Topazius, 

 119 ; ^. Panheiios, 120. 



A. Ralfsii (Sm.). — Disc iridescent, 

 with close radiating series of punctiform 

 granules, interrupted bv numerous subu- 

 late hyaline spaces, which are crowded 

 in the centre and more distant near the 

 margin, where they form irregular rays of 

 doujjle broken lines ; marginal teeth and 

 pseudo-nodule as in A. Ehrenheryii. = 

 Eupodiscus Ralfsii, SBD. ii. p. 86. British 

 coast, (v. 84.) 3. sparsus (Greg, in lit.), 

 granules in loose series, without angular 

 blanks, the principal rays alone reaching 

 the umbilicus, = Eupodiscus sparsus, Greg 

 TMS. V. p. 81, pi. 1. f. 47 : Scotland. 

 " The lines of cellules diminish in num- 

 ber at distinct intervals from the margin 

 towards the centre of the valve, giving 

 a zoned appearance when seen under a 

 low power " (SBD.). A. Ralfsii differs 

 from A. Ehrenheryii in the radiated ar- 

 rangement of its granules, the far greater 

 number of hyaline spaces, and the more 

 irregular distribution of the rays, in 

 which also the blank spaces in the asso- 

 ciated lines are usually alternate. The 

 following remarks on the var. sparsus 

 are condensed from Professor Gregory's 

 papers : — Principal rays equidistant, 

 formed of large dots not closely set ; 

 between the principal rays, the inner 

 ends of which leave a small central imi- 

 bilicus, occur shorter series parallel to 

 each^other, the middle one longest, the 

 others progressively decreasing in length 

 on each side, and the shortest adjacent 

 to the principal rays, which they approach 

 at an angle. Professor Gregoiy finds the 

 same arrangement in A. Ralfsii; but in 

 that form the dots are large and very 

 close. In A. Ralfsii the colom- varies 

 with different shades of purple, blue, 

 green, and yellow, and sometimes brown 

 or buff. At Professor Gregory's sug- 

 gestion, we reduce A. sparsus to the rank 

 of a variety, as he finds the species to 

 vary much in the size of the granules, in 

 their closeness, and in colour. 



A. fulvus (Sm.). — ''Cellular sti'ucture 



indistinct, radiate; colour of dry valve 

 towny.''^ = Eupodiscus fulvus, SBD. i. 

 p. 24,"^ pi. 4. f 40. Britain. Rays obscure. 

 We doubt whether this species be distinct 

 from A. Ehrenheryii, many specimens of 

 which have very indistinct rays. 



A. crassus (Sm.). — Disc somewhat 

 opaque, purplish when dry ; granules in 

 radiating series ; pseudo-nodule as in A. 

 Ralfsii; margin smooth. = Eupodiscus 

 crassus, SBD. i. p. 24, pi. 4. f. 41. Britain. 

 Mr. T. West believes this species to be 

 an immature state of A. Ralfsii. 



Douhtful Species. 



A. Panheiios (E.). — Very large; disc 

 with 120 very fine rays. KSA. p. 128. 

 Cuxhaven. Diam. 1-180". 



* Disc yenerally coloured, furnished with 

 radiating series of puncta. 



A. interpunctatus (Bri.). — Disc with 

 an indefinite number of double rays 

 running from the centre to near the cir- 

 cumference ; the rays composed of short, 

 broken lines; the spaces between the 

 rays are minutely punctate. California, 

 New Zealand, West Indies. = Actino- 

 ptyclms interpunctatus, Bri JMS. viii. 

 p. 94, pi. 6. f. 17. 



A. suhtilis (Greg.). — Disc very hyaline, 

 with numerous very fine inconspicuous 

 radiating dotted lines, a circular punc- 

 tated umbilicus, and rather distant mar- 

 ginal teeth. = Eupodiscus suhtilis, GDC. 

 p. 29, pi. 3. f. 50. Forming brown patches 

 on aides of rocks, llfracombe, Plymouth. 

 This species is easily distinguished by 

 its hyaline appearance in balsam. The 

 pseudo-nodule is minute, radiating lines 

 indistinct, and the umbilicus is furnished 

 with scattered dots surrounded by a 

 dotted circle. Frustules sometimes con- 

 tained in an indefinite mucous stratum. 



2* Disktcith hexayonal cellules, which 

 are not in radiating lines. 



A. tessellatus (Ro.). — Cellules of disc 

 distinct, hexagonal, with a minute no- 

 dule at each angle, not radiant. = Eupo- 

 discus tessellatus, Ro JMS. vi. p. 19, pi. 3. 

 f 1. Pembrokeshire, Hull, Norfolk. 

 Guano. This species is placed in Acti- 

 nocyclus because of its solitary intramar- 

 ginal pseudo-nodule ; but in its structure 

 it differs so much from the other species 

 of that genus, that it might be separated 

 from it. The reticulated disc and ab- 

 sence of rays distinguish it. In balsam 

 it is nearly colourless. 



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