104 Triassic Echinoderms of Bakony. 
Gymnodiadema de LorioL, 1884, genotype G. Choffati de Lor., Lower Callovian, 
has tubercles, and those very small ones, in only two or three rows, adamb- 
ulacral in position, close to the peristome. The rest of the interambulacrum 
is covered with sparse miliaries. 
Scaptodiadema de Loriot, 1891, genotype S. Matheyi de Lor., Rauracian, has relatively 
small main tubercles without definite scrobicule, but separated by secondaries 
which cover all the rest of the surface and are rather irregular and unequal. 
Phalacropedina Lampert, 1900, with genotype H. Guerangeri Cort., a subgenus 
of Hemipedina for «les espéces chauves a hautes plaques, rares granules et 
tubercules attenués en dessus»; it includes also H. calva (Quenst.), ? H. pusilla 
Dames, and ? H. minima Cort. The scrobicular circle is far from distinct. 
Miliaries tend to form scrobicular rings, but are very few in adapica! part of 
test. In the adoral half there are a few secondaries, forming adradial and 
interradial series, but soon dying out. Oxfordian, Corallian. If this has any 
genetic value it no doubt represents a small group arising in Oxfordian times. 
There now remain Hemipedina, Diademopsis, Orthopsis, Mesodiadema, 
Archaeodiadema, Palaeopedina. Unfortunately the distinction between these forms 
is by no means easy to grasp, even when all elements of the test are taken into 
consideration; and it is still more difficult to formulate any differences capable of 
detection in the interambulacrals alone. 
To enter into a complete discussion of these genera would lead us too far 
afield, and it therefore seems better to reserve the account of my investigations for 
a more fitting occasion, and meanwhile to take as starting-point the learned and 
suggestive «Etude sur quelques Echinides de I'Infra-lias et du Lias» by Mr. J. Lampert 
(1900), who has personally examined most of the type-specimens described by 
continental authors. Having, however, myself examined the type-specimens of 
Wricut as well as other specimens in the British Museum, I feel warranted in 
occasionally expressing an opinion different from that of this eminent authority. 
Archaeodiadema J. W. Grecory (1896, Geol. Mag. p. 317) may first be disposed 
of. The only species is A. Thompsoni Grec., Upper Lias, Northamptonshire. 
Lampert (July, 1897, Rev. crit. paléozool.) first considered this as a subgenus 
of Diademopsis, but subsequently (1900, pp. 29—30) as asynonym of Hemi- 
pedina. With the latter conclusion I agree, but on other grounds than those 
of Lampert. He supposed the genus to depend on the simple straight series 
of pore-pairs, and on the imperfect fusion of its majors, leaving free the adap- 
ical primary of each triad. The former character was, it is true, selected by 
Dr. Grecory to distinguish his genus from both Diademopsis and Hemipedina; 
none the less, a faint arcuation of the pore-pairs is shown in his own drawing, 
and, as Lampert points out, the arcuation is no more obvious in many small 
species of Hemipedina: it is, in fact, quite faint even in the genotype, H. 
Etheridgei (holotype, Brit. Mus., E1593). In many early species usually ref- 
erred to Diademopsis the arcuation is only perceptible quite close to the peri- 
stome, e.g. the genotype, D. serialis. The second character mentioned by 
LAMBERT Was not specially described by Grecory, although it is obvious in 
his figure. He did however utilise the compound nature of the ambulacrals 
to distinguish Archaeodiadema from the Orthopsinae, forgetting that, as had 
