Dr. F. A. Bather — I^ew Ophiurid from Cornwall. 161 



IV. — Sympteruba Minvebi, n. g. et sp. : a Devonian Ophiurid 

 FROM Cornwall. 



By F. A. Bather, M.A., D.Sc, British Museum (Natural History). 



(PLATE VI.) 



Description of the Holotype. 



THE specimen (Fig. 6), kindly entrusted to me for description by- 

 Mr. Howard Fox, consists of the oral skeleton surrounded by 

 portions of the disc and of portions of the five rays, all seen from 

 what is believed to be the ventral or actinal surface, and lying on 

 a fragment of the dark slate of the locality, Epphaven. The 

 skeletal parts being preserved in pyrites, it has proved possible 

 to develop the specimen slightly by washing with weak hydro- 

 fluoric acid and then brushing with a soft brush. The specimen 

 is, however, so minute and delicate that this process could not be 

 carried very far. 



The rays vary in length and, to some extent, in the details shown 

 by each. It is therefore convenient to number them in a solar 

 direction from i to v, i being the longest and v the next in length. 

 These numbers are not to be taken as implying any certain 

 orientation. 



Eay i, from its junction with the mouth-parts to the distal portion 

 preserved, is divisible into nine serially homologous segments, of 

 which the ninth or distal-most is incomplete laterally. There is no 

 evidence as to the complete number of segments that originally 

 composed the ray. Those preserved change slightly in character 

 as they approach and enter the disc, which included one of them 

 certainly and a second possibly ; but all show the same elements, 

 except for the lateral spines, which are not borne by the segments 

 within the disc. The lateral spines are borne by the free segments 

 3-8 in groups of three, each group being at the distal outer angle of 

 each segment. The spines of each group diverge fanwise, but the 

 general outward direction of the middle spine of each triad is 

 slightly distal-wards. It is the clear position of these groups of 

 spines which, more than any other feature, enables one to divide 

 this ray into its nine definite segments. Each segment, however, 

 seems capable of subdivision into a proximal and a distal portion 

 (6 and a in Figs. 1 and 2). There is a median body from which 

 proceed two lateral processes or wings on each side. The distal 

 wing has an approximately straight distal margin, lying about at 

 right angles to the axis of the ray, while its proximal margin is 

 deeply excavate. This excavation is clearer in the more distal 

 segments (Fig. 1, p), and its boundary there attains a full semi- 

 circle. The proximal wing of each segment forms the proximal 

 boundary of this excavation, and, in the more distal segments, its 

 distal margin is slightly excavate. In the proximal segments 

 (Fig. 2) this wing appears more like a flattened rod, slightly 

 depressed on its proximal margin, while the distal wing is also 

 like a flattened rod somewhat scooped out on its ventral surface. 



DECADE V. VOL. 11. NO. IV. 11 



