42 



Thouarella moseleyi, Wright and Studer, var. spicata, n. 

 Plate III. figs. 2 and 4. 



Several incomplete specimens, without basal attachment. 



The axis is branched, calcareous in texture, iridescent, cylindrical, and marked 

 by longitudinal ridges and grooves. It is very hard and tough, and on being 

 broken across shows a darker portion in the centre. Its diameter varies from 

 1-1 '5 mm. in the different pieces. 



The twigs arise on the two lateral faces, although here and there a twig may 

 be seen with its origin slightly approximated to one of the other surfaces. 

 They usually curve more towards one face than to the other, and this is ac- 

 centuated by the presence of a polychaete worm lodged on one side of the stem. 

 They are arranged in a roughly alternate manner, but here and there two on one 

 side alternate with one on the other. 



Polyps arise singly and in close proximity on the lateral surfaces of the main 

 stem and branches between the origins of the twigs ; on the twigs they arise in 

 pairs on opposite sides. They are stiff and rigid, rising at right angles to the 

 axis, usually 1'5 mm. in height and from 0'6-0'8 mm. in maximum width. They 

 are covered with flat scale-like spicules, in five transverse and four longitudinal 

 rows. The pre-opercular row of spicules has eight projecting spines which are 

 quite visible to the naked eye, and project considerably beyond the opercular 

 surface of the polyp. The operculum forms a somewhat high cone. 



The general coenenchyma is thin, allowing the axis of the stem, branches, and 

 twigs to shine through. It shows numerous flat scale-like spicules. 



The spicules are flat, irregular multi-tuberculate scales, varying considerably 

 in size and with slightly convex edges. The following measurements were taken 

 of maximum and minimum diameter in millimetres : 



0-6x0-4; 0-45x0-28; 0'28x0'26; 0-14x0-08. 



Some of the spicules bear a long smooth projecting spine, and their dimensions 

 are : 



0-7x0-3; 0-6x0-35 ; 0'5x0'3; 0'4x0'25. 



The tubercles or warts are arranged in a regular manner round the nucleus 

 of the scale, which is always eccentric. The spine projects from a groove, and is 

 very easily detached ; it is sometimes bifid. 



The following table of comparison with the typical Thouarella moseleyi 

 summarises the chief points of difference, on account of which we establish a new 

 and very distinct variety : 



Thouarella moseleyi. Var. spiral a, n. 



1. Twigs alternate. 1. Twigs not strictly alternate. 



2. Polyps in short spirals of three, or 2. Polyps in twos placed almost oppo- 



plar.rd opposite. ate. 



