2 6o THE STELLEROIDEA 



differences are so important, anatomically, that the Ophiuroidea 

 and Asteroidea are often regarded as distinct classes. Owing to 

 the general external resemblance between the two groups, the first 

 naturalists who described them made no attempt to separate them. 

 Thus Linck, who in 1733 (23) figured several Ophiuroids, 

 included most of them, along with some Asteroids, in his genus 

 Stella. The common British species, Ophiura ciliaris, Linn, sp., he 

 named Stella lacertosa, and Ophioderma longicaudu he described as 

 Stella lumbricalis longicauda. He, however, recognised that his group 

 " Stella " must be broken up into several divisions, for he separ- 

 ated Ophiothrix frayilis, 0. F. Miiller sp., under the name of Ilosuht, 

 and the branching forms under the name of Astrophyton. Linnaeus, 

 on the other hand, did not grant the Ophiuroids even generic 

 distinction, and included them all in the genus Asterias. It 

 was not until 1816 that Lamarck (21) definitely founded the 

 genera Ophiura and Euryale. De Blainville in 1834, L. Agassiz in 

 1836, Dujardin in 1840, and Muller and Troschel in 1844, added 

 greatly to the systematic knowledge of the Ophiuroids, which they 

 retained in the order Stellerida. The first proposal to separate 

 the group as one of the primary divisions of the Echinoderms was 

 made by Forbes in 1840 (11); he founded the order " Spinigrada " 

 for the Ophiuroids, while the Asteroids he named the " Cirrigrada." 

 Gray, in 1840 and 1848, kept the two groups as separate orders, 

 but united them in one class, Hypostoma. Since this date the 

 view that the Ophiuroids are a distinct class has been widely 

 adopted. 



The sub-class includes over one hundred genera, most of which 

 are recent. The earliest fossil forms occur in the Ordovician, and 

 representatives are known from all later systems. 



The recent species have been described by many authors, 

 especially by Bell, Diiben, Forbes, Grieg, Grube, Heller, de Loriol 

 le Fort, Ljungman, Liitken, Lyman, Marenzeller, v. Martens, 

 Mortensen, J. Muller, W. Peters, G. 0. Sars, Sladen, Stimpson, 

 Studer, and Verrill. Lyman's report on the Cliallenger Collection 

 is a complete synopsis up to 1882 (31). 



The fossil Ophiuroids are rare, and, as a rule, badly preserved. 

 The literature consists mainly of the description of isolated 

 specimens, as by E. Billings, Bohm, Forbes, S. A. Miller, Pohlig, 

 C. F. Roemer, H. Woodward, Worthen, and Wright. Stiirtz and 

 Roemer have described the remarkable fauna from Bundenbach in 

 Germany, and Salter that from the English Silurian. References 

 to the American Palaeozoic species are given in Miller's North 

 American Geology and Paleontology. 



The first classifications of the Ophiuroids were artificial ; the 

 basis of a natural arrangement was laid by Ljungman in 1867 

 (24). Previous to that date the group had been divided into 



