BRITISH FOSSILS. 



7 



catalogue he remarks on it — " Forme intermediaire entre le M. cor- 

 anguinum et le M. acutus. Les ambulacraires sont dans des sillons 

 plus profonds et plus larges." His figure is a very good representation 

 of a very ordinary and normal specimen of cor-anguinum. Sismonda 

 has cited it also as such without, any more than myself, seeing pecu- 

 liarities in it. 



5. Spatangus punctatus, Lamarck. The figure (tab. xvii.* c. ) of 

 Leske, referred to as representing this species, is an ordinary but large 

 specimen of the normal form ; and we are assured by Agassiz (Echin. 

 Suisse, i. p. 25) that his examination of Lamarck's original specimens 

 convinced him that this, and 



6. Ananchytes semiglobosus, Lamarck, and 



7. Ananchytes spatangus^ Lamarck, are all specimens of cor-anguinum. 

 The true structure of Ananchytes, as contrasted with Spatangus and 

 Micraster, was not understood by Lamarck, whose examination of the 

 Echinidse generally is extremely superficial. 



8. Spatangus acutus, Deshayes (Coq. Caract. des Terr., tab. xi., figs. 

 5 and 6), is regarded by Agassiz and Desor as a distinct species. 

 Judging from the figure, it appears to be a specimen of the normal 

 form of cor-anguinum, in which the caudal extremity is slightly more 

 produced than usual, a variation not uncommon. 



B. " Species^' constructed out of the Rostrated form. 



9. Ananchytes cordatus, Lamarck. Micraster cordatus, Agassiz and 

 Desor. Regarded as distinct also by E. Sismondi. Identical with 

 this is 



10. Spatangus rostratus, Mantell ; and, according to Agassiz and 

 Desor, 



11. Spatangus Requieni, 



12. Scutella pyramidalis, Risso ; and 



13. Spatangus hituricensis, Defrance. 



C. " Species " constructed out of the Gibbous form. 



14. Spatangus gibbus, Lamarck. Micraster gibbus of Agassiz and 

 Desor, but not of the Catalogue Systematique. The figures in the 

 Encyclopedic Methodique (pi. clvi., figs. 4, 5, 6) represent this pseudo- 

 species, which, however, has a far more specific aspect than any of the 

 other varieties. Such extreme examples occasionally occur in England, 

 but are rare. The great development of the postero-lateral ambulacra, 

 resulting from the great elevation of the apex and the low position of 

 the vent, seems, at first, a sufficient distinction, but this character varies 

 much, passes distinctly into the variety next to be named, and through 

 it into more normal types. 



15. Micraster brevis, Desor ; the Spatangus gibbus of Goldfuss, 3Ii- 

 craster gibbus of Agassiz (Cat. Syst.) The intermediate form between 

 No. 14, and more ordinary varieties. It is not uncommon in England, 



