80 GOES, RETICULARIAN RHlZOPODA OF THE CARIBBEAN SEA. 



Textularia Trochus D'ORB. 



Tab. V, %g. 167170; Tab. VI, figg. 171172. 



In his wellknown treatise: Memoire sur les f or amini feres de la craie blanche du 

 Bassin de Paris, Mem. Soc. geol. France 4, p. 45, t. 4, figg. 25 26, D'ORBIGNY has 

 designated a young Textularia, that very much resembles, and is without doubt iden- 

 tical with our form. 



Textularia cuneiformis var. conica WILLIAMS, has been referred by CARPENTER also 

 to Textul. Trochus, but that form is rather a Textul. sagittula, to which also should 

 be referred Textul. conica D'ORB. from Cuba. 



In their admirable work upon the Crag-Foraminifera (Palteont. Soc. 19, tab. 3, 

 figg. 14 16) Messrs PARKER, JONES and BRADY have represented a Textul. agglutinans, 

 with the chambers divided nearly in the same manner as in the West Indian form, 

 with which it also agrees in the shape of aperture and base, but its general shape and 

 features are those of a common Textul. agglutinans. 



The same Authors' Textul. trochus (Pal. Soc. 19, tab. 3, figg. 17 18) may be 

 identical with our form, but may also prove to be a Textul. sagittula. 



The Caribbean form is remarkable for its compressed and more or less spread 

 out or fanlike shape, when of a more advanced age. The plane of this compression is 

 quite contrary to that of the commonly known Textularia in as much as the zigzag 

 boundary-lines, marking the septa are found on the edges. It agrees in this respect 

 perfectly with D'ORBIGNY'S Cuneolina from lower Cretaceous formation (For. Bass. tert. 

 Vienne p. 253, t. 21, figg. 50 52) and is an intermediate form between that repre- 

 sented species and the common Textularia. It has sometimes the margins of its long 

 fissure-like aperture here and there quite closely approached one to another and grown 

 together, shewing thus a tendency to the same arrangement of a row of small aper- 

 tures, as we find in Cuneolina. 



Our form is very compact and thickwalled, tightly agglutinated of the finest de- 

 bris of chalk; the surface is quite smooth and covered with fine pores. When laid 

 open along the flat central space between the two rows of chambers, which space 

 is formed by their apertures, the long chambers are exposed to view. They consist 

 of, first a shallow vestibule occupying the whole breadth of the inner part of the shell: 

 then at the back of the vestibule a row of a few deep impressions or shallow cham- 

 bers, each of which has about four short channels leading out of it. These channels 

 branch off into about the same number of short tubes and these again terminate in 

 from 3 to 5 very fine porecanals. In this way a system of 4 different sets or orders 

 of branching cavities and channels are produced. Each set of ramification is ordina- 

 rely arranged in pairs, one pair being placed above another. Such a regular arrange- 

 ment as the mentioned is however far from invariable, for it happens sometimes, that 

 the first ramification is only di- or trichotomous and the second and third may be va- 

 riable in like manner. Occasionally too a part of a chamber or even a whole chamber 

 is found to be destitute of one or other of the sets of channels. 



