﻿192 ASTROPHYTON COSTOSUM. 



covei'ed by a close pavement of flattened grains ; it is very distinct 

 from the sides and upper surface, which are beset with fine rounded 

 grains, and are sej)arated from the lower surface by a sunken line. 

 Along the upper surface of the arm runs a distinct median furrow. 

 Radial ribs running quite to the centre of the disk, prominent, their 

 outer ends cut abruptly off, making a concave scar ; length to breadth, 

 17:4; they are closely beset with microscopic, thorny stumps or grains, 

 some of which end in three or four distinct thorns. The same thorny 

 grains are found, but smaller and more scattered, on the interbrachial 

 spaces below, and a few also on the depressed parts of the upper sur- 

 face of the disk. At the tips of the arms and on the smaller twigs 

 there are, as usual, double vertical rows of grains, bearing hooks. 

 Tentacle-scales one or two, small, and difficult to see, extending inward 

 as far only as the fourth fork of the arm. Color, in alcohol : above, 

 dark purplish-brown, varied with black ; below, interbrachial spaces the 

 same ; under surface of arms much lighter. 



LIST OF SPECIMENS. 



Astrophyton costosiim Seda. 



Astrophyton costosum Seb.\ (noii Linck). III. PI. IX. Fig. 1, p. IC. 1758. 



Euri/ale muricatum L.\mk. An. s. Verteb., II. p. 538. 1816. 



Aslrophi/lon muricalum Agass. Mem. de la Soc. lies Sciences Nat. Neuchatel, p. 12. 1839. 



Astrophyton muricatum. MiJLL. & Trosch. Syst. Asteriden, p. 122. 



Astrophyton muricatum Lutken. Addit. ad Hist. Oph., p. 156. 



Special Harks. — Disk purplish brown. Radial ribs sharply and 

 much raised, bearing a few large fleshy spines, whose sides are often 

 fluted. 



Description of a Sjwcimen. — Diameter of disk, 58""" ; from outer 

 side of madreporic shield to outer corner of opposite mouth-slit, 28""°' ; 

 Avidth of arm at base, 24"""-. Length of arm and distances of its forks 

 from each other, — 



