COCCASTER BULBIFERUS. 75 



slightly more numerous than the infero-marginalia in the proximal portion of the 

 arm, but from the sixth infero-marginal onwards they become equal in number 

 and alternate with the infero-marginalia. In the arm figured the adarnbulacralia 

 are turned slightly outwards, so that the nose which fits upon the ambulacral ridge 

 is brought into view. This accounts for the shape figured. The remaining arms 

 show, on the other hand, the adarnbulacralia in the usual position, namely, with 

 the nose hidden. 



One of the ambulacrals may be seen at the extremity of the arm. It is oblong, 

 and has the customary ridge. 



Measurements. — r is 3*4 mm. Width of arm at base is 4"8 mm. 



Horizon and Locality. — This specimen was found in the lane to Gelli Glrin 

 Farmhouse, 2^ miles south-east of Bala. The zone is given by Ruddy as that of 

 " Stvopliomena e.vjxuisa,^' which, according to Bather (91, p. vi), is situate just above 

 the " Little Ash " of the Geological Survey Memoirs, at the base of the Bala series. 



Genus COCCASTER, novum. 



Generic Characters. — Disc covered with moderately large plates consisting of a 

 centrale surrounded by five intermediate plates, which are again enclosed by ten 

 large primary radialia and interradialia. Adambulacralia considerably more 

 numerous than the infero-marginalia. Odontophor almost pentagonal, with a 

 re-entrant angle at its base. 



The genoholotype and only species is C. hulbiferus, n. sp., from the Lower 

 Ludlow (Silurian) mudstones of Leintwardine, Herefordshire. 



The fact that the genus is found in the Silurian, makes it later than any 

 " Hudsojinster" described by Schuchert. It has five accessory plates on the disc 

 instead of the six or seven often found. The shape of the odontophor is also 

 peculiar. It may be a late offshoot from the " Hudsonaster " stem. 



1. Coccaster bulbiferus, n. sp. Plate II, fig. 1 ; Plate III, fig. 2; Text-figs. 33, 



38, 39. 



Material. — Both the imprint of the apical surface and its counterpart are 

 known, and these specimens comprise the sole known material of the species. 

 The former is in the Scottish National Museum (65/158a), the latter in the Ludlow 

 Museum. 



Apical Surface. (Plate II, fig. 1 ; Text-fig. 38). — The cast of the imprint 

 of the apical surface is very clear, and shows the ossicles with but little displace- 

 ment. There is a large centrale surrounded by a circlet of five intermediate 

 plates. Outside these, again, are the large primary radialia and interradialia. 

 The primary interradialia are flat and breastplate-shaped. In the reconstruction 

 they are figured as being symmetrically arranged round the disc. In the specimen, 



