yan. 20, [887 



NATURE 



267 



THE BLASTOIDEA 

 Catalogue of the Blastoidea in the Geological Depart- 

 ment of the British Museum {Natural History) ; with 

 an Account of the Morphology atid Systematic Position 

 of the Group, and a Revision of the Genera and Species. 

 By Robert Etherid^c, Jun , and P. Herbert Carpenter, 

 D.Sc, F.R.S. Illustrated by 20 Lithographic Plates, 

 &c. (London : Printed by Order of the Trustees, 

 1 886.) 

 'T'HIS important memoir is in all but in name a mono- 

 graph of the interesting group of extinct Echino- 

 derms first called Blastoidea by Thomas Say in 1825. It 

 originated, the authors tell us, some seven years ago, in a 

 desire to investigate the structure and relationships of this 

 group by the light of the recent advances made in our 

 knowledge of their living representatives. 



Echinoderm structure owes much to the genius and 

 labours of Johannes Midler, and a knowledge of the results 

 of his inquiries largely influenced Prof. F. Roeraer in pre- 

 paring his classical work on the Blastoidea. Recent 

 investigations have added enormously to our knowledge 

 of the structure of the Stalked Echinoderms, so that a 

 renewed morphological examination of their extinct allies 

 was in every way desirable, and this we have now before 

 us. The authors were indebted for much kindly aid in 

 the examination of specimens to a whole host of friends, 

 among whom it seems desirable to mention more 

 especially Mr. Wachsmuth, who sent from America a 

 selected series of forms from his fine collection of 

 American Blastoidea, thus enabling the authors to form 

 their own views on many points of structure. He also 

 supplied them with recent information as to the pro- 

 gress of his own investigations among the American 

 species. 



The memoir begins with a chapter on the biblio- 

 graphical history of the group, commencing with the 

 paper by Say in the Journal of the Philadelphia Academy of 

 Natural Science for 1885. Roemer's monograph appeared 

 in 1852. Billings, in 1869, published a series of important 

 memoirs, in which he suggested that the remarkable 

 lamellar tubes beneath and between the ambulacra 

 appeared to have served the function of respiration, 

 and designated them as " hydrospires ; " the sum- 

 mit openings in connection with them were called 

 " spiracles." Wachsmuth's valuable contributions com- 

 menced in 1877, while in 1882 the present authors 

 began a series of memoirs, which have now culminated 

 in the present work. A second chapter treats of the Stem 

 and Calyx. The stem of the Blastoidea would appear to 

 be but little known, since individuals in which the stem 

 remains attached to the calyx are rarely found. Mr. 

 Wachsmuth has a slab of Pentremites, in which three 

 specimens have stems of between 5 and 8 inches in 

 length, and the best preserved stem examined by the 

 authors is figured as occurring beneath the calyx of 

 Granatocri?ius iwruwodi, where it is seen to consist of 

 some small thin discoidal joints, which are so little 

 characteristic, that if found isolated it could not be cer- 

 tainly said whether they belonged to a Blastoid or a 

 Crinoid. Though all the Blastoids may have had stems 

 in their early stages, some appear to have had no stem 

 in their adult state. It will be remembered that the 



adult Comatula shows no trace whatever of having at one 

 time been a stalked form. The calyx is described at 

 great length and with great clearness, and the views of 

 Wachsmuth and others are criticised. Chapter III. is 

 devoted to the study of the Ambulacra, and the fourth 

 chapter to the Summit Plates. These latter were first dis- 

 covered by Owen and Shumard (1850) forming a conical 

 covering of small plates over the oral and ovarial apertures 

 on a specimen of Pentremites godoni. With the exception 

 of Hambach, no recent pateontologist disputes that these 

 plates are an integral part of the organisation of a 

 Blastoid. The chapter on the Hydrospires and Spiracles 

 is full of interest. The former can in no way be re- 

 garded as a respiratory portion of the ambulacra! system, 

 while the analogy of recent Crinoids goes to show that the 

 ambulacral groove of the Blastoids was a ciliated food- 

 groove, and that it was not occupied by any portion of the 

 generative system ; but the authors adopt Ludwig's com- 

 parison of the marsupial pouches (genital bursK) of 

 Ophiurids with the Blastoid hydrospires. The zoo- 

 logical position of the Blastoids is still regarded 

 as a subject of discussion, though it would seem 

 that Say's opinion is correct, and that the Blastoidea 

 may be regarded as a group intermediate between the 

 Crinoidea and Echinoidea. As to the distribution in 

 time, there is no certain evidence of the existence of true 

 Blastoidea anterior to the Upper Silurian period, and it 

 is curious that all the known species of this period are 

 confined to North American strata. The Devonian rocks 

 of the British Islands have yielded but imperfect traces 

 of them. The Lower Devonian rocks in France and 

 in Belgium have each yielded a single Blastoid, but the 

 great centre of their development in Europe during this 

 geological period was in the north of Spain. In North 

 America they were, on the contrary, largely represented, 

 both in generic and specific forms. Regarding the 

 Blastoids of the Devonian system from a general point of 

 view, the number of genera was largely increased at the 

 close of the Silurian period, and all the families are to be 

 found represented in the Devonian period. Pentremites, 

 which is the type form of the class, did not make its 

 appearance until the Devonian. The Carboniferous rocks 

 of the British Islands are rich in Blastoid forms, which 

 are also to be found in Belgium, and were well developed 

 in the sub-Carboniferous rocks of North America. No 

 Blastoid is common to America and Europe, and in 

 Europe the range of specific forms is very limited, though 

 one species is found common to the Devonian of Spain 

 and Germany, and one to the Carboniferous rocks of 

 Britain and Belgium. 



A most useful stratigraphical list of all known species 

 arranged geographically, is given, and then follows the 

 descriptions of the species, to which it is not needful to 

 allude further than to state that the greatest care has 

 been taken, not only with the diagnoses, but with the 

 synonyms and the distribution. A copious index and 

 twenty beautifully executed plates complete the volume. 

 Some sixteen of the plates were drawn on stone by the aid 

 of a grant from the Government Grant Fund of the Royal 

 Society, and, with the approval of the Council, and 

 certainly to the advancement of science, were transferred 

 to the Trustees of the British Museum, by whose order 

 this " Catalogue " has been published. 



