806 



SYSTEMATIC HISTOKY OF THE INFrSOKiA. 



in 1-1152". EM. pi. 33. 12. f. 6. Siberia 

 and Oregon. Ehrenberg's figiu'es scarcely 

 differ from those of B. Lamina, except 

 in being narrower. 



B. Lancea (E.). — Lateral valves lan- 

 ceolate, with subacute apices, and 3 to 8 

 parallel transverse stride m 1-1152". EM. 

 t. 33. 12. f. 5. Oregon. Twenty-seven 

 septa in each frustule. 1-336". 



B. Castellum (E.). — Lateral view of 

 central portion elliptic, with obtuse ends, 

 and four marginal imdidations. EM. 

 t. 38. 2. f. 1. Siberia. 1-900". Lateral 

 valves unknown, (iv. 44.) 



B. ? gihhum (E.). — Frustules smooth, 

 bacillar; 2 to 4 together, with straight 

 centre ; lateral view gibbous at the 

 middle. KSA. p. 117. Kurdistan. 

 1-1152". A doubtful member of this 

 family. 



Species hnown to us only hy na^ne. 



B. CMense (Eh. Chili.).— " Kelated to 

 B. compressimi,^^ EM. p. 301. 



B. constrictum (E.). — Fossil. North 

 Asia. 



Genus GOMPHOGRAMMA (Braun). — Filaments compressed, continuous, 

 of few frustules ; septa clavate, alternate, nearly equal ; lateral valves elliptic, 

 furnished with straight transverse costas. Aquatic. Gomphogramma agrees 

 with Tetracyclus in its freshwater habitat and in the strong transverse costae 

 of its lateral valves, but differs (as we believe, essentially) by its clavate septa, 

 which are not continued as costoe across the central canal. We are not suf- 

 ficiently acquainted with the structure of Biblarium to decide what may be 

 its relation to that genus ; but it is not improbable that further investigation 

 may requii^e their union. Professor Smith thus contrasts Gomphogramma 

 with Tetracyclus : — '' In Tetracyclus the valve is cruciform, and the costae 

 arched ; in Gomphogramma the valve is ellij)tic, and the costse direct ; but 

 these seem rather to belong to specific than generic characters, and the pro- 

 priety of uniting these genera hardly admits of a question " (ANH. January 

 1857). 



GoMPHOGBAMMA vnpestre (Bravm). — 

 Frustules subquadrate, with fi'om one to 

 three septa on each side and gland-like 

 dots along the junction-margins. Braun 

 in Rab D. pi. 33. t. 9. Freiburg ; Pyre- 

 nees. This seems to be a mountainous 

 species, and most probably its detection 



would reward a search in our alpme 

 districts. In its clavate septa it some- 

 what resembles Tei-psinoe, but the re- 

 semblance is merely superficial ; for the 

 septa in that genus are transverse, and 

 in this longitudinal ; consequently they 

 belong to different groups. ( )y i^i,) 



Genus TETRACYCLUS (Ralfs).— Filaments free, elongated, inflated at 

 the centre, striated ; striae continued across the inflated centre ; septa equal ; 

 lateral surfaces costate. Aquatic. The inflated centre and strongly costate 

 lateral surfaces sufiiciently characterize this genus. '' The genus Biblarium, 

 constituted by Ehrenberg in 1845, appears to differ from the present merely 

 in the solitary character of its frustules ; and this character arises from the 

 fossil nature of the gatherings from which Ehrenberg derived his specimens. 

 I feel assured that all the species are filamentous in a living state, and that 

 the greater number of them are casual varieties of Tetracyclus lacustris" 

 (SBD. ii. p. 37). 



Tetracyclus lacustris (Ralfs). — La- 

 teral view with the inflations and ends 

 roimded. SBD. ii. p. 38, pi. 39. f. 308. 

 = Striatella Thienemanni, EA. p. 136; 

 Biblarium Stella ; B. Glans and B. spe- 

 ciosum, EM. pi. 33 ; B. strumosum, EM. 

 pi. 33. 2. f. 13. Recent, Britain and 

 Iceland ; fossil, Oregon and Siberia, 

 (xi. 24, 25,). The median inflation seems 

 variable ; it is sometimes so much de- 



veloped as to form a crucial figure re- 

 sembling the quaterfoil of a Gothic win- 

 dow, but sometimes merely a slight 

 swelling, as in Bihlanum speciostwi (E.).fyff 



T. emarginatus (E,, S.). — Inflations 

 deeply notched, otherwise like T. lacus-- 

 tris, SBD. ii. p. S8. = Bihlarium emargi- 

 natum, EM, pi. 33. 2. f. 6. Recent, Britain ; 

 fossil, Siberia and Mexico. 



T. elegans (E.). — Inflations acute. = 



