180 



THE GEOLOGIST. 



the same horizontal plane, whilst in the Poteriocrinus there are two which extend 

 beyond the others, as I have already remarked, in 1852, in my "Recherches sur les 

 Crinoides " (p. 85). The anal plates are small, and a trifle less bowed than the 

 others. The surface of all these plates is perfectly smooth. All the other parts 

 are unknown to me ; but the articulation of the base with the stem demonstrates 

 the latter to have been very slight. Dimensions. — The length of the calix is only 

 gmm^ its diameter that of the base b^'^, that of the stem l-5m'». 



Affinities and Differences. — This species resembles very much my 



Hydreionocrinus (Poteriocrinus) Maccoyanus, from which, however, it 



will not be difficult to distinguish it, by reason of the very decided 



convexity of the different plates of the calix, and the feeble dimensions 



of the stem. 



Position and Locality. — This species has been discovered in the 

 environs of Glasgow, in a black schist, subordinate to the carboniferous 

 limestone with Productus giganteus and Spirifer bisulcatus. I owe 

 the knowledge of it to Mr. Salter, Palseontologist to the Geological 

 Survey of Great Britain, so well known for a great number of impor- 

 tant researches. 



Explanation of figures. — PI. lY : — 



Fig. 6. — Calix, seen from the side of the base, slightly enlarged. In the collec- 

 tion of the Geological Survey at London. 



Fig. 7- — The same, seen in profile, of natural size. 



The following is the description of a third crinoid, very remarkable 

 for the globular form of its calix, which I dare not place definitely 

 amongst the Hydreionocrini, because it diff'ers in its general character, 

 and because the upper parts of the bulb are unknown to me. I am not 

 more able to class it, in a certain manner, among the Poteriocrini, as it 

 differs from most of them in the form and perfectly horizontal position 

 of its radial plates, which are all, as in the true Hydreionocrinus, placed 

 on the same plane. 



3. Hydreionocrinus ? globularis. Be Koninch. PL lY., fig. 1 — 4. 



The Calix of this pretty species is of ordinary size, and of sub-sphoeroidal form, 

 slightly elongated at its base. Its surface is perfectly smooth, and the sutures of 

 the various plates scarcely perceptible, and not indicated by any depression or 

 groove. The basal plates are all nearly of the same form, producing by their union 

 a small star with five well-marked rays. The articulation of the stem is situated 

 in the hollow of a small, round, shallow ditch. The sub-radial plates are very 

 lai"ge and slightly, also, broader than long. Four of them have a tolerably regular 

 hexagonal form ; the fifth has seven sides, of which one is welded to the anal plates. 

 The first radial plates, those only which are known to me, offer three different forms, 

 the three most distant from the anal side are similar one to another ; they are 

 pentagonal, and one a little broader than long. Of the two last, that which is placed 



