242 R. Etheridge, jun. — On Ramipora in the Caradoe. 



A reference to the Plate will show that the habit of the polyzo- 

 arium is clearly that of Ramipora, as distinguished from Synocladia, 

 a central or chief stem from which are given off a series of straight 

 non-bifurcating branches, without any separation by longitudinal 

 ridges or keels, beyond that occupying the centre of each stem or 

 branch, and the cells all opening much on the same level; instead 

 of, as in the latter, a series of continually dichotomizing branches, 

 longitudinally divided by several carinse separating the cells. 



The polyzoarium in this interesting Polyzoon was probably openly 

 infundibuliform, or basket-shaped, there being a series of the princi- 

 pal straight stems, all branching off at the base from a common 

 root, or stolon, but in no way bifurcating or springing from one 

 another. Four of these stems are shown in the larger specimen, 

 each giving off laterally, and at subalternate distances, the secondary 

 stems, which, as in the former case, in no way bifurcate or dichoto- 

 mize, but proceed direct, and intact in themselves, to the periphery 

 of the frond. Here and there however, between two of the secondary 

 stems, similar short (or abortive ?) ones arise from the main stem, 

 which unite directly with the cross-bars or dissepiments. As in 

 most of these frondescent Polyzoa, the common root is devoid of 

 pores or cell-openings. 



From the secondary stems are given off the interstices, or cross- 

 bars, by the union of which are formed the mesh-openings, or what 

 in a Fenestella would be called the fenestrules. These dissepiments 

 spring from opposite sides of each secondary branch at an acute 

 angle, and on a level with one another, and uniting more or less in 

 the middle line between every two contiguous secondary branches, 

 with those arising from the latter give rise to the broadly v- sna P e( l 

 fenestrules. As a rule, great regularity may be noticed in the form 

 of these openings, taking the whole surface of the frond, but here 

 and there an irregularly-formed one is to be met with. The section 

 of the main stems, secondary branches, and dissepiments was bi- 

 angular or diamond- shaped. 



The angular or apical ridge of the various stems and branches of the 

 frond is devoid of any pores, or other features of interest ; but on the 

 sides of the main stems, immediately under the apical ridge, are two 

 linear rows of contiguous pores or cells with round apertures, those 

 of the one row being a little subalternate with those of the other. 

 There may be a third row, but I have not been able to distinguish it, 

 and from the width of the lateral portions of these stems I hardly think 

 there is room for the expansion of the cell-mouths. The description 

 of the arrangement of the cells on the main stems will also suffice 

 for that on the secondary stems and the interstices — for I cannot 

 detect any difference in their distribution. The reverse face of the 

 frond is, as before said, angular, but non-celluliferous. 



So little has been done in this country towards the elucidation of 

 Silurian Polyzoa, with the exception of the brief original descrip- 

 tions, mostly by Lonsdale, and scattered through the works of 

 Murchison, 1 that there is always the chance of re-describing or re- 

 1 And those contained in Prof. M' Coy's Brit. Pal. Fossils. 



