KONGL. SV. VET. AKADEMIENS HANDLINGAR. BA 



m) 25. 



N:o 



119 



uj) the dorsal median line of the sac. This series, together with half the width of the 

 series on either side of it. forms a flat or smoothly rounded back to the sac and is nn- 

 disturbed by plication; but the other series form longitudinal ridges, one to a series, 

 between which the plates are folded. This folding also affects the outer halves of the 

 plates on either side of the median dorsal series (fig. 165). The ridging and plication 

 increase with age up to a certain point when they again disappear: this senile character 

 is increased by the greater wear that has affected large specimens [see Text-lig. 17 (3)]. 

 The plication in fuU-grown specimens is nearly the same as that of B. cucurbitaeeus but 

 not so marked. 



The Tegmen is shown in figs. 167, 168, 169. The plates are small and irregular, 

 with no definite arrangement. 



Fi<r. 1. 

 Fiir. 2. 



Fi*. 3. 



Fig. 4. 



Fig. 5. 



Fkr. C. 



Text-fig. 17. Structure in Botryocrinus. 



The anal area of B. decadactylus ; (X 3 diam.) 



From tln' proxiraal part of the Veutral Sac of /;. cucurbitaeeus, specimen b. To show the folding, 



without perforation, of t lie plates. The distal end <>\' the sac is beyond the left of the drawing. 



( X •'. diam.) 

 Part of the Ventral Sac. as seen from the back, of B. ramosissimus, specimen b. (X 3 diam.) 

 Ventral snrface of Arm of Ii. ramosissimus, specimen c To show small irregular covering-plates. 



(X 9/8 diam.) 

 Distal part of Stem of 71. decadactylus, K. 1412 B. M. To show irregularity of pentameres. (x 12 diam). 

 Root of B. decadactylus, K. 1412 B. M. (X 3 diam.) 



The Stem in matlire or old specimens is round. In specimen b (fig. 160) it is 

 marked with rather strong interradial and fainter radial ridges, so as to be obscurely 

 pentagonal. It is coraposed of ven' thin ossicles about 0.25 mm. high, with occasional 

 intercalated ossicles half or less than half the size, occupying onlv a part of the cirele 

 (figs. 162, 163). Beside these intercalated ossicles there are occasional evidences of longi- 

 tudinal sutures. The eanal is pentagonal, and in a stem of ."> mm. diameter has a dia- 

 meter of about 1.5 mm. 



