ABTEU<>II>K \ 01 SDKTH PACIFIC AM) UU\ kTBRfi II-1IKK 121 



to Q 7 mm. and arc broader at top than ui base The finer itructura is characteristic 

 Tin- vtTtii-al ridges carry expanded bladelike, hyaline, -harp thornleta, more de- 

 veloped than those of h ex a c ti a 



The abactinal skeleton i- compact and the groups of Bpinelete are usually arrai 

 in fairly definite longiseries, frequently interrupted ami often not al all regular on the 

 dorsolateral p] > In typical specimens there is a broad oarinal band of -pinelets, 

 upward of 10 to a plate, and on either Bide the equivalent of two dorsolateral Beries, 

 ihat next d> the Buperomarginals the more regular There are three dorsolateral 

 longiseriea of papular urea-, Bmaller than the platee Dorsolaterals with from one to 

 -ix spinelets. Plates not to be differentiated without preparation 



Superomarginals broad, the Beries bending upward at base of ray; plates armed 

 with a vertical (transverse l angular series, <>r shallow chevron, of five to i-i^-h t Bpinelete 

 proximalrj (four or five in smallish specimens] and about five distally (two or three 

 in -in ii 11 examples). Spinelets similar to but slightly larger than the dorsolaterals and 

 usuallj slightly bent as in Plate 17, I • la. The superomarginal band of spinelete 

 is broader but less compact than the carina!. 



[ntermarginal channel verj narrow, [nferomarginal plate-- with two occasion- 

 ally three) Bpinelete, the upper subequal to largest superomarginal spines, the lower 

 spine usually much larger, flattened and aubtruncate at ti|>; Bometimee both are 

 enlarged, especially distally Knd of Bpinelete slightly upcurved. In compn 

 spinelete the ventral border is curved as in s broad-tipped knife, while the upper 

 border is Btraight, or onlj slightly upcurved, Sometimes the spinelets are sub- 

 Bpatulate Proximal plates may carry only one spine. 



< me series of actinal platee extends three-fourths to four-fifths K, and each i 

 carries a single Bpine very similar to the larger inferomarginal. A second Beries of 

 Bmaller plates, armed each with a small -pine (about size "f Bmaller inferomarginal), 



extend- m Large specimens al t two-fifths to over half K. and 1- abeenl in most 



small 'ui. - 



Adambulacral plates variable The plate- of proximal third or half of ray have 

 one and two -pine- in irregular alternation, Bometimes continuing to near end of ray; 



or the plates of outer pull have only one spin,.; the proximal plates, Or a majority, 

 may carry two -pine- while the distal are alternately inonaeanthid and diplaeanthid. 



or else only monacanthid ; or else all the plate- are monacanthid with the exception of a 

 few scattered diplaeanthid plates proximally. In a Beries of monacanthid plates 



alternate ones have a -lenderer, more tapered spine BOmewhat advaneed into the 

 furrow These plates lack the outer -pine of the COUple. The other plate-, lacking 

 the furrow spine, carry a -oinewhat heavier BUbclavate or BUbepatulate spine, usually 

 turned away from the furrow The tir-t two or three pairs of adambulacral plate- Hfe 



in contact interradially, First plate somewhat longer than second 



Mouth plates of the usual small size For form and armature BOB Plate 47. 



While the longer of the two aetinostomia] spines is usually as long or 



a little longer than the plate, there i- considerable individual variation, and specimens 



from Monterey Hay may have this Bpine considerably shorter than the plate The 

 Buboral spines are u-uall\ a little longer than the ndoral adambuhicral -pin. 



Papulae in small area-, few to an area, but rather conspicuous in li\ hilt specimens 

 There are about three dorsolateral loieji-eric-, one intermaru'inal and two nctmal 



