Notes on Cambridge palaeontology. IV. Some new Upper Greensand echinoderms / by Harry Seeley.
- Harry Govier Seeley
- Date:
- 1861
Licence: Public Domain Mark
Credit: Notes on Cambridge palaeontology. IV. Some new Upper Greensand echinoderms / by Harry Seeley. Source: Wellcome Collection.
Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.
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![Cidaris gradata. Greatly inflated, flattened below, with the peristome circular j ele- vated above, with the periprocte pentagonal. Arabulacral areas nearly one-third of the width of the interambulacrals, sinuous, and divided into two parts by a deep mesial groove ■, furnished with four rows of rather large granules, which are not arranged in straight transverse lines. Poriferous zones deeply im- pressed on the base, furnished with a close row of granules, which are rather smaller than those of the intermediate spaces; they divide the pairs of pores. The ambulacra are narrow at the apex, so that the inner rows of granules are suppressed; they become a little narrower towards the mouth. Inter- ambulacral area with two rows of rather convex plates, of three and four each. The tubercles are small on the base, and progressively increase in size, so that the scrobiculse of the uppermost of the ‘ three-series^ occupies half the width of the area. The uppermost plate of the ‘ four-series ’ is small and granulated, or has only a rudimentary tubercle. The areolae are circular, moderately impressed, placed below the middle of the plates; margined by two rows of large granules of about thirteen each, an inner row forming the margin of the pit, and an outer row between these, which does not reach to the margin; thus both rows appear to form one irregular circle. The bosses are truncated cones, which are propor- tionally elevated inversely to their size. The tubercles are large depressed spheres. Miliary granulation coarse, on the upper part very large, so that a line of not more than twelve would be sufficient to reach across the widest part of the largest plate. Nearly \ inch high, more than | inch wide; oral aperture | inch, apical aperture y’’-g inch. Differs from C. Heberti (Desor) in wanting the character “ scrobicules petits et serresfrom C. dissimilis (Forbes) in the more elevated form, four rows of ambulacral granules, wide ambulacra, &c. It is common, perhaps commoner than C. Sedgwickii, but in general only occurs in detached plates. A single beautifully perfect example is preserved in the cabinet of J. Carter, Esq. Cidai'is Sedgwickii. Inflated, elevated [rather subconical ?]. The ambulacral areas are narrow and sinuous. The poriferous zones much im- pressed, and rather narrower than half the intermediate taper- ing space; they have a row of granules down the middle, sepai-ating the two rows of pores : towards the apex the gra-](https://iiif.wellcomecollection.org/image/b22412426_0011.jp2/full/800%2C/0/default.jpg)
