OCR Text |
Show 652 ON SOME FORAMINIFERA FROM TRINIDAD. [Nov. 6, closely embracing. Sometimes each successive chamber embraces all the previous ones ; in other cases some of the initial chambers are visible as indistinctly marked annular segments. A thread-like ridge, like a flange, surrounds the sphaeroid in the direction of its length. This ridge, which often appears to be double, expands at the larger end of the test, and its two elements separating, leave between them a fissurine aperture. This is an elongated narrow opening between twx> pouting lips, the lips being a continuation and extension of the ridge or flange. Many specimens show a ridge at right angles to the longitudinal ridge ; but this is produced by the breaking-away of the last chamber at the line of suture. This singular organism appears to differ in some essential characters from any Foraminifer hitherto known, at least so far as I have been able to find out. It varies in shape from an almost perfect sphere to a sphaeroid of very prolate shape, the initial (aboral) end being sometimes a very rounded and blunt projection. The longitudinal ridge is sometimes obsolete towards the aboral pole, sometimes it is single, and occasionally it is triple, the two lateral elements being the most raised. In shape the test resembles a very round Glandulina, like G. obtusissima, Beuss (Tert. Foram. Fauna, 1863, pi. viii. fig. 93 ; also 67. globulus, figs. 94, 95), or G. abbreviata, Neug. (Sherborn and Chapman, London Clay Foram., Journ. Microsc. Soc. 1886, pi. xiv. fig. 20), or a Lagena like L. obtusa, Egg. (Beuss, ' Lagenideen,' 1862, pi. vii. figs. 92, 93). The test is hyaline, glistening, and very fine and close-grained in texture. It has only been found in the Ditrupa-oed of Pointapier, Trinidad. EXPLANATION OF PLATE XLI. Fig. 1. Amphicoryne-form of Nodosaria hispida, D'Orb., var. 2. Cristellaria aculeata, D'Orb., var. A form found abundantly in the Ditrupa-bed of Pointapier, Trinidad. Closely allied to C. wetherellii, Jones, and C.fragaria, Grumb. Compare also Marginidina cristella-rioides, G-iiinb. For comparison with fig. 1. 3. Frondicularia complanata, Defr. Flabelline variety showing Cristellarian initial portion. 4. Frondicularia alata, D'Orb. {complanata, Dei'r.). Specimen showing (a) Cristellarian initial portion, and (b) portion reproduced after loss by fracture of the original oral portion. 5. Frondicularia flabelliformis, n. sp. Usual form. In many specimens the ends of the chambers project more than is shown in this drawing 6. Frondicularia flabelliformis, n. sp. A thicker and stouter form than the preceding. This may be compared with F. spissa, Terquem (Rupert Jones, ' Monthly Microscopical Journal,' 1876, pi. cxxviii. fig. 24). 7. Initial segment of Polymorphina, comparable with Lagena globosa, Mont. 8, 9. Specimens showing tbe development of Frondicularia from a Polymorphina segment. These may be compared with Flabellina ponderosa and triquetra, Terquem (Rupert Jones, ' Monthly Microscopical Journal,' 1876, pi. cxxviii. figs. 25, 26). 10. Stilostomella rugosa, n. sp. A specimen with a protuberant neck. 11. The same. A specimen with a less protuberant neck. 12. Ellipsoidina subnodosa, n. sp. 13. Ellipsoidina exponens, Brady, M S . |