552 



proximally encroach upon the adambulacrals and sometimes push be- 

 tween them (thus separating the adambulacrals one from another] and 

 border the furrow. 



Off Oregon, 786 fathoms. Bottom, green mud. 



Ceramaster clarki new species. 



General form stellato-pentagonal but last 2 or 3 superomarginals 

 in contact medially. General aspect somewhat resembling C. patagonicus 

 (Sladen), but margins much thinner, marginal plates smaller, their 

 granules coarser, hemispherical, and slightly spaced, the abactinal plates 

 with fewer and larger granules, more numerous and slightly larger 

 pedicellariae; the actinal intermediate plates with smaller and less 

 regular plates (especially in the series adjacent to adambulacrals), and 

 larger, less regular, thimble-shaped granules; adambulacral plates with 

 subequal, robust, truncate tubercular spinelets in the first actinal series 

 instead of granules, and the plates narrower than long, instead of wider 

 than long. Furrow spinelets 4 or 5, compressed, and longer than plate. 

 R 53 mm; r 33 mm; R 1,6 r. 



Bering Sea (54° 30' 30" N. Lat.; 179° 14' E. Long.), 344 fathoms. 

 Bottom, greenish brown sand. 



This species differs from C. leptoceramus (Fisher) in lacking secon- 

 dary abactinal plates, in having coarser actinal and marginal granules, 

 much coarser and fewer abactinal granules to each plate, fewer and 

 longer furrow spinelets, and in having the first series of the actinal 

 adambulacral spinelets well developed and tubercular. From C.Jajwnicus 

 (Sladen], clarki differs in all these points (except secondary abactinal 

 plates); especially striking are the differences in abactinal and actinal 

 granulation , and in the form and armature of the adambulacral plates. 

 In C. arcticus (Verrill) the adambulacral plates are very short, more 

 than twice as wide as long, and furrow spinelets are only 2 or 3; the 

 papulae are usually not single (as in clarki) but 2 to 4 in each group, 

 the interradial abactinal plates are lobed, never in clarki. 



Named for Dr. Hubert Lyman Clark. 



Cladaster validus new species. 

 Arcuately pentagonal with slightly convex abactinal surface; broad 

 marginals with tumid naked abactinal surface ; regular abactinal plates 

 bearing spaced, deciduous obovoid granules and spatulate pedicellariae 

 of small size; with 2 furrow spines and 1 larger heavier davate spine on 

 surface of adambulacral plate; with unequal actinal intermediate 

 granules and relatively large broadly spatulate pedicellariae. R 17 mm; 

 r 10 mm; R 1,7 r. 



