V. Botryocrinus. 395 



length as about 6 centim. Ossicles, both of main arms and 

 armlets, slightly moniliform. 



Costals 4 to a ray, except in left anterior radius, where are 

 only 3. Lower edge of first costal slightly curved to fit facet 

 of radial ,• the remaining sutures are horizontal. The first 3 

 costals are of about the same height, viz. 2'3 millim., and are 

 45 millim. in greatest, 3*75 millim. in least width. The 

 fourth costal is axillary and pentagonal, 4 millim. high and 

 5 millim. in greatest width. 



The armlets are given off from the main arms, on alternate 

 sides, either on successive ossicles, or usually on every second, 

 occasionally on the third ossicle. The ossicles from which 

 they are given off differ little from the axillaries of a dichoto- 

 mous arm. The armlets are of very varying size; they have 

 primary and sometimes secondary branches, but do not appear 

 to branch quite as much as in B. ramosissimus (PI. XIII. 

 fig. 3). 



The ventral side of the arms is unknown. 



Anal structures : — Radianal is broken, but was apparently 

 normal. 



Anal x or Brachianal 4*5 millim. high and 3'75 millim. 

 wide. 



The ventral sac itself is not seen. The proximal median 

 plate of the sac is apparently an irregular hexagon ; it occupies 

 nearly the entire width of the anal x } so that, on its right side 

 at all events (in this specimen), no smaller lateral plate rests 

 on the anal x. Its height is 3 millim., its width below, 3*75 

 millim. Above it is seen to support 3 small plates, and these 

 are followed by others apparently alternating with them. 



This species is at once distinguished from B. decadactylus 

 and B. pinnulatus by the presence of armlets, the irregular 

 character of the arms, and the shape of the cup. It differs 

 from B. cucurbitaceus in the thick low arm-ossicles. From 

 B. ramosissimus , which it otherwise closely resembles, it 

 differs in the beaded shape of the arm-ossicles, for those of 

 the Swedish species have as a rule concave sides, and in the 

 presence of 3 or 4 costals instead of 1 or 2. From all species 

 it differs in the high proximal median plate of the sac. 



Botryocrinus decadactylus, sp. n. 

 (PL XIII. figs. 5-15.) 



Cyathocrinus (sp. 2) decadactylus, Salter, Catalogue of Cambrian and 



Silurian Fossils &c, p. 123 (Cambridge, 1873). 

 Cyathocrinus (sp. 3) quindecimalis, Salter, op. tit. p. 124. 



This species is founded on a large number of specimens, of 

 which the most important are as follows : — 



