68 Triassic Echinoderms of Bakony. 
Genotype: T. princeps NEuMAyR. 
Revised diagnosis of Lysechinus (based on the observations of Grecory). 
A Tiarechinid in which the single peristomial plate of each interambulacrum is 
succeeded by a horizontal row of two plates abutting on the ambulacra and the oculars 
and this by a horizontal row of three plates, the outer ones abutting only on the 
oculars, and this finally by a horizontal row of three plates. the outer ones abutting on 
the oculars and the genitals. 
Genotype: L. incongruens GREGORY. 
Tiarechinus ? sp. 
(Plate VI, fig. 128.) 
Material. — A fragment, adherent to matrix, from the Cassian beds of Cserhat 
(Leitnerhof). 
Description of the Specimen. — Height, 87mm. Width, 6.5 mm. 
Along one margin are 12 rounded projections, each about 0.8 mm. wide, and 
rising slightly above the generalsurface. At one end, the lower in fig. 128, this margin 
seems to bend sharply round on itself, and there is a slight elevation at the angle. The 
remaining surface of the fossil is covered with small pustules (? tubercles), irregular in 
size and arrangement; and between them is a very fine granulation (? miliaries). 
Relations of the Specimen. — Itis with great hesitation that I refer this 
exceedingly obscure fragment to Tiarechinus, and | do so largely because there is no 
other form which it suggests either to me or to others who have kindly examined it. 
The absence of any appearance of definite sutures, even after prolonged treatment 
with glycerine and alcohol, is no evidence to the contrary; indeed a more vivid imagin- 
ation might interpret as sutures the markings or cracks which are to be detected with 
some difficulty. The general ornament is similar to that onthe interambulacrals and 
plates of the apical system in Tiarechinus. The interpretation provisionally suggested 
is that the fragment is the greater part of an interambulacrum, of which the adambula- 
cral border is preserved on one side (the right in fig. 128). The projections on this 
border are supposed to be more prominent tubercles alternating with the ambulacral 
plates. It is possible that the sharp bend at the end of this border represents the 
adapical end of the ambulacrum, in which case the oral end has been placed uppermost 
in fig. 128. The curvature of the fragment is not unlike that shown in Loven’s figures 
153, 154; but if the specimen be Ziarechinus, it represents a form at least twice the 
size of any Tiarechinid hitherto described. 
Famity: CIDARIDAE. 
Equals Section I of Cidaridae Duncan (J. Linn. Soc., Zool., XXIII, p. 26; 1889), as restricted by 
J. W. Grecory («Treatise on Zoology», ed. LANKESTER, III, p. 302; 1900.) 
Triadocidaris. 
1887. Triadocidaris L. DOEDERLEIN: «Japanischen Seeigel», p. 39. 
1900. Triadocidaris Dorp., J. LAMBERT: Bull. Soc. Sci. l'Yonne, LIII, p. 44. In addition to MUNSTER 
1841, and Laue, 1865, see also 
1887. L. DoEDERLEIN: N. Jahrb. f. Mineral. 1887, II, pp. 1—4, pl. i. 
1896. A. Tornauisr: N. Jahrb. f. Mineral. 1896, II, p. 42. 
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