PALEONTOLOGY. 393 



The systematic study and morphology of the Pelmatozoa 

 was greatly advanced by J. S. Miller's Monograph of the 

 Crinoidea, which masterly work constructed a secure basis for 

 all future inquiry into the morphology of the group. Miller 

 made application of the architectural arrangement of the plates 

 in the calyx as a basis of classification, and recent researches 

 have frequently found it advantageous to revive leading features 

 in Miller's classification. 



Goldfuss and Miinster added a number of new specific 

 descriptions to the knowledge of Crinoidea, but made no 

 attempt to elucidate the structural relations. Three important 

 memoirs were contributed by the anatomist, Johann Miiller, on 

 the structure of Pentacrinus (1841), on Comatula (1847), and 

 on the structure of Echinoderms generally (1853). These 

 memoirs were published in the Transactions of the Berlin 

 Academy, and for several decades formed the groundwork of 

 further zoological investigations in this group. Miiller included 

 the study of fossil forms in his researches, and he sub divided 

 the known Crinoidea into three sub-orders Tesselata, Arti- 

 culata, and Costata. 



Almost simultaneously with Miiller's works there appeared 

 in England a monograph of fossil and recent Crinoids by the 

 two Austins (1843). But in spite of many new and valuable 

 observations, this work was unsuccessful, on account of its sub- 

 division of Crinoids into stalked and unstalked groups. This 

 sub-division was regarded as quite artificial, seeing that the 

 gifted zoologist, Vaughan Thomson, had in 1836 demonstrated 

 the development of the genus Comatula from a larval stage 

 resembling a stalked Pentacrinus. 



The anatomical structure of the living Pentacrinus was 

 described by Liitken (1864), and that of the Comatulids was 

 elucidated by the researches of Wyville Thomson (1865) and 

 W. B. Carpenter (1866). The deep sea explorations off the 

 coast of Norway led to the discovery of Rhizocrinus, and the 

 detailed investigation of this interesting genus, carried out by 

 Sars (1868) and Ludwig (1877), met with a cordial reception 

 in palaeontological circles. 



Numerous monographs and shorter papers on Palaeozoic 

 Crinoidea were meanwhile being published ; among the more 

 voluminous writers on this subject were De Koninck and Le 

 Hon (1854), Hall (1847-72), Roemer (1860), Ludwig Schulze 

 (1866), Meek and Worthen (1866-75); Mesozoic Echino- 



