858 



ST8TEMATiC HISTOEY OF THE INFUSORIA. 



not confined to Amphitetras. Professor Smith, indeed, remarks, " The pro- 

 jection of the connecting membrane beyond the suture of the valve is a cii-- 

 cumstance which meets us for the first time in Amphitetras ; " but we believe 

 that this occurs in every genus in which the new portions of the dividing 

 frustiiles are formed within the persistent central portion, and in this respect 

 there is no perceptible diiference between Triceratium and Amphitetras. As 

 some species have been placed in Amphitetras solely on account of their 

 quadrate form, the correctness of their position is consequently not free from 

 doubt. 



Amphitetras antediluviana (E.). — 

 Lateral view with straight or concave 

 margins ; angles roimded, each with an 

 apparent opening ; cellules large, radiat- 

 ing, and concentric. Living, Denmark, 

 England, America, &c. ; fossil, Oran, 

 Greece. (xi. 21, 22.) A. tessellata, 

 Sh TMS. ii. /3, sides very concave ; 

 the cellules on the central portion are 

 smaller, and arranged in longitudinal 

 lines. 



A. Adriatica (K.)- — " Lateral view 

 quadrate; cellules radiating and con- 

 centric; primary sides plane." KSA. 

 p. 134. Adriatic Sea. 



A. parallela (E.). — Cellules in lateral 

 \dew large, arranged in parallel lines. 

 Fossil. Greece. 



A. crucifem (Kitton, n. sp.). — Valves 

 punctate, and marked by a line passing 

 from the centre to each angle. Front 

 view deeply constricted on either side of 

 connecting zone. Valves minute, with 

 slightly convex sides, and produced 

 mammiform angles. Cleanings of shells 

 from West Indies. Distinguished by 

 the cruciform lines of the valve, which 

 taper fi'om the centre to the angles. 



where they terminate in points. We 

 have seen 4 or 5 frustules connected by 



the angles. 



Doubtful or imperfectly known Species. 



A. ornata (Sh.). — "Size small, mar- 

 gins concave, and folded so that each 

 valve is not imlike in form to a col- 

 legian's cap ; surface somewhat iiTegu- 

 larlv ornamented with delicate vein-like 

 markings." TMS. ii. p. 16, pi. 1. £ 10. 

 Natal. Var. /3, with 5 angles, (vm. 16.) 

 This is probably a state of some veined 

 species of Triceratiimi. 



A. favosa (Harv. & Bail.). — " Sides 

 scarcely concave ; lateral view quadran- 

 gular ; angles almost straight, scarcely 

 produced ; surface tessellated with large 

 hexagonal cellides." Proc. of Acad, of 

 Philadelphia, 1853. Mindanao. 



A. Crux (Bri.). — Valves cruciform, 

 with the angles widely rounded ; sm-face 

 coarsely punctate. Cleanings from shells, 

 West Indies; Californian guano. Bri 

 JMS. vii. p. 181, pi. 9. f. 13. This may 

 be a 4-angled var. of Triceratium castel- 

 lation or T. trisulcuni. 



Genus AMPHIPENTAS (Ehr.). — Frustules free, simple, cellulose or gra- 

 nulate, pentagonal. Probably pentagonal forms of Triceratium. 



AisiPHiPENTAS aUernans (E.). — Sides 

 concave; angles obtuse; the angles of 

 the external pentagon alternating with 

 those of a smaller central one, which has 

 a circular umbo at its middle. KA. 

 p. 134 ; EA. p. 122, pi. 2. 6. f. 9. Cuba. 

 (XI. 32.) 



A. Pentacrinus (E.). — Pentagonal ; its 

 dorsal sm-face presenting a striated ring. 

 Diam. 1-240". KA. p. 134. Fossil. 

 Greece. Fragments like Amphitetras. 



K.jiexuosa (B. MS.). — Sides four or 

 five, gibbous ; angles conical ; sm'face 

 flat; cellules hexagonal, covered by 

 minute puncta. Gulf-stream, (a'i. 22.) 

 From drawings by Professor Baile3\ 

 " Under a low power, the markings 

 appear circular, as represented in the 

 figures" (B. j. The margins are undulated 

 in consequence of their gibbous projec- 

 tions, as in Triceratium Pannula, and may 

 be 4- and 5-angled forms of that species. 



FAMILY XIL— TEEPSINOE^. 



Frustules quadrangular, smooth, compressed, fui^nished with unequal trans- 

 verse costae or incomplete sej)ta interrupted at the middle. We have sepa- 

 rated this small group from Striatelleae because, notwithstanding the great 



