138 E. GROVE AND G. STURT ON 



T. repletum, Grev. (" T. M. S.," Vol. xiv, p. 83, PI. 9, Fig. 18). 

 — Very rare. 



T. plumosum, Grev. (" T. M. S.," Vol. xii, p. 85, PL 10, Fig. 4). 

 — A form has been observed resembling this in all respects except 

 that pseudo-nodules are present. We prefer to class it as Gre- 

 ville's form rather than to introduce confusion by making a new 

 species of it. 



T. condecorum, Ehr. (Schm. "At!.," PI. 76, Fig. 28).— 

 Scarce. 



T. trisulcum, Bailey (" Prit.," p. 854, PI. 8, Fig. 27).— Not 

 scarce. 



T. barbadense (" T. M. S.," Vol. ix, p. 44, PI. 4, Fig. 12).— 

 This species occurs rarely, but appears to agree with Greville's 

 authentic examples. The figure above cited is not good, and we 

 append one. (PI. XI, Fig. 24.) 



T continuum, Grev. («T. M. S.," Vol. xii, p. 13, PI. 2, Fig. 7). 

 — Very scarce. 



T. (Stictodiscus) parallelum (Ehr.), Grev. — A form of this with 

 seven angles has been found by Dr. Gray, and the same indefatig- 

 able observer has discovered an oval form of the var. gibbosa, with 

 acute ends, resembling in outline a Biddulphia, of which we give a 

 figure. (PI. XIV, Fig. 28.) 



T. shadboltianum, Grev. (Sch. " Atl.," PI. 80, Figs. 18-20).— 

 Small forms, with three flat processes, apparently of this species, 

 occur here. 



Lampriscus ? debit, n. sp., Gr. and St. — We place this singular 

 form in this genus with great hesitation for the present. 



Hitherto only two specimens have been observed, and we are 

 indebted to Julien Deby, Esq., for first calling our attention to it. 

 It is to be hoped that further examples will be discovered, from 

 which the true character of this diatom can be ascertained. Valve 

 circular, with two large marginal processes (?) opposite each other, 

 between which occur smaller marginal processes (?) unequal in 

 number (on the one side three, on the other four). The centre is 

 flat, with a clear umbilicus, on which is a group of spines, the rest 

 of the surface being covered with curved lines of dots, which con- 

 verge towards the bases of the processes (?) somewhat as in Aulis- 

 cus. Diam. -0055". (PI. XI, Fig. 27.) 



N.B. — The figure shows the valve as viewed from the inside, as 

 the specimen was mounted with that side uppermost. 



