bo 
Cr 
M. A. Pomel on the Classification of Echinida, — 2: 
Fig. 5. Bairdia formosa, seen from left side. 
Fig. 6. The same, seen from above. 
Fig. 7. The same, seen from the front. 
Fig. 8. Loxoconcha alata (male), seen from left side. 
Fig. 9. The same, seen from above. 
Fig. 10. The same, seen from below. 
Fig. 11. The same, seen from the front. 
Fig. 12. The same (female), seen from left side. 
ig. 13. The same, seen from below. 
Fig. 14. Cythere crispata, seen from left side. 
Fig. 15. The same, seen from above. 
PLATE XV. 
Fig. 1. Paradoxostoma(?) reniforme, seen from left side. 
Fig. 2. The same, seen from above. 
Fig. 3. Cytherura acris (male?), seen from left side. 
Fig. 4. The same, seen from above. 
Fig. 5. Cythere favoides (male), seen from left side. 
Fig. 6. The same (female), seen from left side. 
Fig. 7. The same, seen from above. 
Fig. 8. Cythere Speyeri (male), seen from left side. 
Fig. 9. The same (temale), seen from left side. 
Fig. 10. The same, seen from below. 
Fig. 11. The same, seen from the front. 
Fig. 12. Cythere dissimilis, right valve, seen from the side. 
Fig. 13. The same, seen from above. 
[All magnified 40 diameters. ] 
XXV.—Observations on the Classification of Echinida, to 
serve as an Introduction to the Description of the Tertiary 
Fossil Echinodermata of Western Algeria. By A. POMEL*. 
I HAVE had the honour to present to the Academy a series of 
lithographic drawings representing some fossil Echinodermata 
from Algeria, which are to form a part of the paleontology of 
that country. The descriptive part of the work is not yet 
printed; and I now submit to the judgment of the Academy 
the introduction to this work, im which I propose certain mo- 
difications in the classification followed by authors. 
The number of the series of coronal plates, sometimes 
twenty, or two in each area, in the true Echinida, sometimes 
much greater by their multiplication in the interambulacral 
areas, and even in the ambulacral areas in the Tessellata, 
gives a first division, of the rank of a suborder. 
The Echinida present three types, which advance regularly 
from the bilateral to the radial symmetry, and which I 
name Spatiformes, Lampadiformes, and G'lobiformes. The 
first have the mouth placed very eccentrically in front, and 
the anus behind ; the obliteration of the anterior ambulacrum 
* Translated from the ‘ Comptes Rendus,’ Aug. 3, 1868, pp. 802-305, 
