NATURE 



509 



THURSDAY, APRIL I, l5 



FOSSIL ECHINODERMS 



Handbttch der Palaontologie. Unter Mitwirkung von W. 

 Ph. Schimper, Professor an der Universitat zu Strass- 

 burg, herausgegeben von Karl A. Zittel, Professor an 

 der Universitat zu Miinchen. I. Band, iii. Lieferung. 

 Mit 195 Original-Holzschnitten. (Miinchen: R. Olden- 

 bourg, 1879.) 



MORE than three years ago a notice appeared in 

 these columns (vol. xiv. p. 445) of the first Part of 

 a new treatise on Palaeontology by Professors Zittel and 

 Schimper. Of the first volume, that which is devoted to 

 Palaaozoology, and is from the pen of Prof. Zittel, three 

 Parts have now been published. The last one, which 

 deals with the fossil echinoderms, fully justifies the great 

 expectations to which the first gave rise, both text and 

 illustrations being of a very high order of excellence. 



It commences somewhat abruptly in the middle of a 

 sentence belonging to the introductory chapter on the 

 sub-kingdom generally, the earlier pages of which appeared 

 at the end of Part 2. At the end of the volume, in like 

 manner, there are four pages which contain the first 

 portion of the chapter on the Vermes. 



Like most Continental writers, Prof. Zittel divides the 

 Echinoderms into four classes only, viz., Crinoids, Star- 

 fishes, Urchins, and Holothurians. The first class is a 

 large one, including the Cystids and Blastoids, as well as 

 the true Crinoids, or Eucritwidea, as Zittel calls them ; 

 and very nearly half the book is devoted to it, while the 

 Urchins take up the greater part of the remainder. 



Each class is treated separately as regards its general 

 anatomy, terminology, classification, and distribution, 

 both in space and in time. Besides the numerous refer- 

 ences scattered through the text, a valuable bibliographi- 

 cal list is appended at the commencement of every section 

 but that on the Holothurians, to which, for obvious 

 reasons, only one page is devoted. In the sections on the 

 Urchins and the Crinoids the results of the Challenger 

 Expedition (so far as published) are fully considered, and 

 attention is drawn to the analogy between the recent 

 Comalula and the palaeozoic Crinoids in the very limited 

 geographical distribution of individual specific forms, and 

 in some cases even of genera. 



The chapter on the general anatomy of the Crinoids is 

 fairly complete, except as regards the blood-vascular 

 system, and exceedingly accurate on the whole, though 

 we must take exception to the passage on p. 329, in which 

 it is stated that all {sammtliclu) living Crinoids have a 

 central mouth and an excentric anal opening. Nearly 

 forty years ago Midler described several Comatula with 

 an excentric mouth and a central anal tube. Thi 

 been since grouped into the genus Actinomclra, which 

 includes quite one-third of the species of recent Comatulce. 

 Almost the only recent work on the Crinoids to which no 

 reference is made is Ludwig's singular suggestion that the 

 genital plates of the Urchins and Asterids are homologous, 

 not with the genitals of the Ophiurids and the basals of 

 the Crinoids, as hitherto supposed, but with the oral 

 plates of both these groups. Probably, however, this is 

 only because Ludwig's paper was published too late to 

 Vol. xxi. — No. 544 



receive the notice which it deserved. To this same category 

 of oral plates Dr. Zittel refers the remarkable " Consoli- 

 dations-Apparat " in the calyx of Cupressocrittus and the 

 corresponding plates which lie above and alternate with 

 the radials in Cyaihocrinus and allied genera. This 

 appears to us to be a very probable explanation of the 

 homologies of these plates; and we wonder that the so- 

 called "deltoid pieces" of the Blastoids are not regarded 

 by Prof. Zittel in the same light, for they occupy precisely 

 the same position between the radials and the central 

 mouth as the oral plates of Cyaihocrinus. 



Schiiltze's views as to the subtegminal mouth of the 

 ic Crinoids are of course fully adopted, but the 

 author does not altogether follow Wachsmuth's arrange- 

 ment of the group according to the three principal plans 

 upon which the vault is constructed ; for the vault of the 

 Taxccrinidcc is described as resembling that of the 

 Cyatlioaiiiiihc. whereas, according to Wachsmuth, the 

 structure of the vault is essentially different in the two 

 families. Prof. Zittel also accepts Schultze's views as to 

 the position of the boundary line between the plates of the 

 arms and those of the calyx; and he brings forward a strong' 

 piece of evidence in their favour, namely, that according to 

 Dr. Carpenter's observations the first radials of Comatula 

 correspond es-entially in their origin and mode of growth 

 with the basals and orals, appearing as plate-like films 

 from the first, and that they therefore belong to the 

 calyx. On the other hand, according to Sir Wyville 

 Thomson, the second and third radials do not, like the 

 first, begin as expanded cribriform films, but first appear 

 as horseshoe-shaped spicula or imperfect rings ; and Dr 

 Carpenter has shown that the origin and development of 

 the arm-joints is of essentially the same character. As in 

 the Urchins and Starfishes, therefore, the calyx normally 

 contains but two rows of plates, viz., the radial series above, 

 and below them the inter-radially situated basals ; though 

 in some Crinoids there is a third series of plates, the under- 

 basals, which occupy a radial position between the true 

 basals and the top stem-joint. 



The author's descriptions of the arms and their append- 

 ages do not seem to us to be always quite consistent. 

 In the Comatula with ramifying arms all the branches are 

 equivalent. Each of the ten primary arms may fork and 

 give rise to two equal secondaries. Each of these again 

 may bear two equal tertiary arms, and so on, the succes- 

 sive di\ isions forking altogether perhaps five or six times, 

 and the two divisions borne by any axillary being equal 

 to one another. In some of the stalked Crinoids, how- 

 ever, this regular forking ceases with the second axillary, 

 which bears, not two equal tertiary arms, but a smaller 

 one that remains undivided, and a larger one that con- 

 tinues the line of the secondary arm and ends in an 

 axillary joint. This also bears two unequal arm-divisions, 

 and the same mode of branching is continued on each 

 successive axillary. These smaller lateral branches, 

 which may always be on the same side of the main arm 

 Dusk, or may alternate on opposite sides, are termed 

 "Nebenaste " by Zittel, who rightly states that they appear 

 when there is no forking. There is therefore a little incon- 

 sistency in his describing the arms of Cyaihocrinus and 

 Euspirocrinus as many times or repeatedly forked, while 

 in the diagnosis of the family the arms are described as 

 having " Nebenaste," and the figures of both genera show 



