REVISION OF PALEOZOIC STELLEKOIDEA. 51 



greatest expansion is brought about by the introduction of more and 

 more accessory disk pieces between the adambulacrals and mframar- 

 ginals. The beguming of this development of the secondary skeleton 

 is seen in Petraster and is variously progressive in the dill'erent species. 

 They finally crowd more and more distally into the rays, as may be 

 seen in Vranaster and PalxosteUa. Among the large-disked Crypto- 

 zonia, as Schucliertia and the Palasteriscidse, it is the ambital and 

 abactinal accessory pieces that go to enlarge the arcs and body cavity. 



CLASSIFICATION. 



A good history of the various attempts at classifjong the fossil 

 starfishes is given by Spencer (1914:39-52). How recent starfishes 

 are classified may be learned from VerriU (1914:24), and it will be 

 seen that his principles are not always applicable to fossil forms be- 

 cause of the loss of parts through fossihzation. In subsequent pages 

 the author will give his groupings up to superfamilies, but the time 

 is not yet at hand for an ordinal classification applicable alike to 

 fossil and recent starfishes. 



Catalogue of Paleozoic S teller oidea. — A catalogue of all Paleozoic 

 starfishes was published by the writer in April, 1914, under the title 

 "Fossilium Catalogus, Animalia, part 3, SteUeroidea palasozoica," pp. 

 53 (Junk, Berlin). It gives the entire bibliography of the genera and 

 species up to that date, and an outline of the classification adopted. 

 The actual date of several new genera is of the work above cited, 

 although they are also printed m the present book as new. This 

 Bulletin is there cited as of 1914 and is now to be corrected to 1915. 

 The above-mentioned catalogue will always be useful for ready refer- 

 ence to the literature, although the larger volume repeats all of the 

 essential references, corrected to November, 1914. 



DESCRIPTION OF GENERA AND SPECIES. 



Class STELLEROIDEA. 

 Subclass ASTEROIDEA. 



PHANEROZONIA Sladen. 



Asteroidea nearly always with large marginal plates. These consist 

 in the Mcsozoic and later asterids of completely superposed inframar- 

 ginals and supramarginals; in the Paleozoic the rule is that the in- 

 framarginals alone border the animal, while the supramarginals are 

 always dorsal, generally alternate \vith the inframarginals, and are 

 placed farther inward though resting more or less upon the latter. 



Ambulacrals always present and opposite in arrangement in post- 

 Paleozoic forms. In the oldest and most primitive Paleozoic forms 

 they are apt to be alternate tlu-oughout the rays, or only so distaUy 

 in the young parts. By far the greater number of Paleozoic forms, 

 however, have the opposite arrangement. 



