242 BULLETIN 88, UNITED STATES NATIONAL MUSEUM. 



"Ambulacrals alternating in adjoining columns, while the neigh- 

 boring ambulacrals and adambulacrals are directly opposite each 

 other. The margin of the disk is concave and limited by a row 

 of more or less conspicuous simple [not two rows of superposed] 

 marginalia restricted to the disk. The sides of the free rays are 

 bounded by adambulacrals. These and the ambulacrals are [common 

 to the two sides of the animals, and abactinally are] roughly sculp- 



tured, usually naked, and only 

 in rare cases were adambulacral 

 spines observed. Madreporite 

 actinal, situated near the peri- 

 stome in one of the interradial 

 ~ I " c ' areas nearest to the left adam- 



FIG. 28. AMBULACKALIA AND ADAMBULACRALIA OF bulacrals of a radius. 7 ' (Sch6n- 

 ENCRINASTER ROEMERI, AFTER SCHONDORF. a, AP- A^^t lain "\ 



- ' ' 



PEARANCE OF THE PLATES WHEN CRUSHED OR OB- 

 SCTTRED BY CLAY. EACH AMBULACRAL HERE APPEARS 



AS IF OF TWO PIECES; b, SAME BETTER PRESERVED -,-j- (^ O l r lf 11 ^ G. prm q 

 OR MORE CLEANED; c, THE ACTUAL FORM OF THE ossi- noLai ^ ss - ^ e 



CLES WHEN WELL PRESERVED AND COMPLETELY to the Lower Devonic of Rhenish 





Germany. 



Remarks. This well-known genus has been referred to the asterids 

 and to the ophiurids, and though it has most often been placed 

 among the true starfishes, it now appears to belong to neither of 

 these orders. Schondorf has restudied the material with great 

 care and has made out the detail of the ambulacralia, with the 

 result that he erects for Aspidosoma the order Auluroidea. In 

 the work of 1910 cited above the matter is set forth in great detail, 

 and all that can be done here is to direct atten- 

 tion to the more important of his illustrations, 

 with their descriptions, reproduced in part here 

 and on pages 213 and 214. 



As Aspidosoma was first used for a genus of 

 reptiles, it can not, under the rules of nomen- 

 clature, be used again for another group of 

 animals. It is possible, however, under the FIG. 29. ORAL SKELETON OF 

 rules to make use of Enerinaster, but in doing ^7*^"! 



SO the proceeding should first be explained. MUCH ENLARGED. AFTER 



Encrinaster was proposed by Haeckel as fol- SCHONDOEF - 

 lows : In defining his sixth order of asterids, the Crinastra or lily stars, 

 forms that he said already had crinoid characters, he cited as exam- 

 ples of it Protaster sedgwickii and P. = Aspidosoma arnoldi. These 

 forms, he added, are so different from Protaster miltoni ( i that we here 

 separate the former as Encrinaster (E. sedgwickii, E. arnoldi, etc.)." 

 Under ordinary circumstances it would be best to disregard the 

 name because of the inadequate definition, but as Aspidosoma is 

 preoccupied, we are obliged to propose another name to take its 



