CARADOCIAN CYSTIDEA FROM GIRVAN. 403 



^ 189. The tag process, which is borne at the outer angle of the leg by marginals 

 1 and 12, was attached to the frame either by suture or possibly by articulation (G22, 

 PI. III. fig. 30). Its distal portion is bent away from the heel over the opening of 

 the leg, and seems to have been flattened. 



§ 190. The tongue process is supported mainly by marginal 11 and partly by 

 marginal 10, and was perhaps joined to them by articulation (G22, Gr26, PI. III. figs. 

 30, 26). It is much longer than the tag process, is bent in the same direction, that is, 

 away from the leg-opening and towards the toe, and is often flattened in the plane of 

 extension (G26, G45, G53). In G64, where the actual stereom is preserved, the 

 tongue appears to be about half as thick as it is wide. 



§ 191. All the marginals, except for their various spines and processes, have a cross- 

 section of somewhat U-shape, and to each edge is attached the flexible Integument 

 bearing minute plates. The integument of the reverse face is likewise attached along 

 the edges of the strut, and along the under-edges of the broad extensions that meet at 

 the top of the leg. The integument of the obverse face stretches over the whole area 

 within the frame, and passes across the top of the leg. The reason why there is no 

 extension of the frame in this region on the obverse face is that here lies a definite 

 opening in the integument (§ 199). 



§ 192. The plating of the integument is not the same all over. The plates appear 

 to have been a trifle larger on the reverse face than on the obverse (G6) ; those within 

 the leg-half are often rather larger than those in the foot-half; and within the foot- 

 half the plates nearer the sole are smaller than those above (Gl4). All these plates 

 appear as a rule to be irregular, flattened, and tessellate, but in the leg-half they 

 frequently show signs of imbrication {e.g. G41, G46, PI. III. fig. 37). In the leg-half 

 of G45 there are about nine plates within 4 sq. mm. (PI. III. fig. 31). 



§ 193. On the obverse side the plating appears invariably to consist of larger, 

 rounded, slightly swollen plates surrounded by smaller plates, as well shown in G42 

 and G 45 (PL III. fig. 31). The arrangement is not exactly regular, except that 

 sometimes near the margins the plates are set parallel to the frame, but it is of 

 the same nature throughout and not imbricate. The appearance is just that of a 

 rather roughly grained bookbinder's morocco. In G45 (PI. III. fig. 31) there are 

 nine of the larger plates with an indefinite number of the intercalated smaller plates 

 within 4 sq. mm. 



There are, however, on the obverse side two important modifications of the plated 

 integument, one connected, I believe, with the intake of the food-current (§ 195), the 

 other with its outflow (§ 199). 



§ 194. Traces of the original Stereom of some marginals, of the tongue, and of some 

 mtegument plates, as well as of the proximal region of the stem, are preserved in G64. 

 From this and from G26, one gathers that the stereom of the marginals and longer 

 processes was finely fasciculate. 



I 195. The modification for the Subvective System lies on the obverse face, 



