40 BRITISH PALEOZOIC A8TER0Z0A. 



of Wales, and Hall and Billings obtained mncli of their material from tlie Trenton 

 (Ordovician) Limestone of New York and Ottawa. 

 The following g-enera and species were known : 



Paleeuster, Hall. Palasterina, M'Coy. 



Paheaster asperrimvs, Salter. Palasterina 2^)'ii>iR'va, Forbes. 



Palivaster obtusus, Forbes. Palasterina antiqua, Hisinger. 



Palasasfer coronella, Salter. Palasterina stellata, Billiugs. 



Palivaster ruthveni, Forbes. Palasterina nujosa, Billings. 



Palivaster hiriido, Forbes. Pet raster, Billings. 



Palxaster niagarensis. Hall. Petraster rigidus, Billings. 



Palxaster sp., undescribed, from Devon. Protaster, Forbes. 



Palmaster mattitina, Hall. Protaster tepfosoma, Salter. 



Palseocoma, Salter. Protaster mil ton i, Salter. 



Paleeocoma coivini, Salter. Protaster salteri, Sowerbv. 



Palieoconia cygnipes, Salter. Protaster sedgwichi, Forbes. 



PaUeocoma marstoni, Salter. Stenaster, Billings. 

 Sub-genus Bdellacoma, Salter. Stenaster pulchellus, Billings. 



Bdellacoma vermiformis, Salter. Stenaster salteri, Billings. 



Sub-genus Mhopalocoma, Salter Tieniaster, Billings. 



Rhopalocoma 2)yrot€c1inica, Salter. Tieniaster cylindricus, Billings. 



Palxodiscus, Salter. Tieniaster spinosus, Billings. 



Palieodiscvs ferox, Salter (since shown to Lepidaster, Forbes. 



be an Echinoid). Lepidaster grayi, Forbes. 



The folloAving forms are also. mentioned : 



Asterias avti.qiia, from the Silurian rocks in the State of Tennessee. 



Asterias rhenana, Johannes Midler, from the Devonian Sandstone at Coblentz. 



Asterias constellaia , Tliorent, 



Asterias oldusiis, Goldfuss, from the Mnschelkalk of Wiirtemberg. 



Wright omitted to mention Cmlaster latiscntatiis, G. and Fr. Sandb., and Aspi- 

 dasoma arnoJdi, Goldfuss, both from the Devonian of Germany, This latter form 

 was with great insight stated by Johannes Midler (52) to be closely related to 

 Protaster, Forbes. 



Wright, following the views of Salter, placed all the above genera among the 

 Asteroid ea, although he admitted that Txniaster had relations with the Ophiu- 

 roidea (p. 34). Salter, in his first paper (57), had noticed the obvious resemblance 

 of the general body-form of Protaster miltoni to the Ophiuroidea, and had placed 

 it in that group. Later research (58) convinced him that the madreporite was 

 dorsal, and he transferred the form to the Asteroidea. 



This earlier work is, as may be expected, lacking in detailed observation. 

 Workers then were not concerned with theories of evolution, and Avere usually 

 satisfied with generalised descriptions, which, taken with the figured specimens, 

 would allow identification of specimens in cabinets and museums. Few attempts 

 were made to distinguish between the important component ossicles, c. g., the 



