246 DISCOVERY REPORTS 



high arched, the inferomarginals, close to the single adambulacrals, defining border of 



the subplane actinal surface. 



Description. The abactinal and lateral pustules are very small and numerous, closer 

 together than the space between. Nearly all of them enclose a small crossed pedicellaria 

 of one size, 35-38 mm. in length. The lowermost series of these small pustules repre- 

 sents the superomarginals. At end of ray the last i or 2 pustules have a tiny central 

 spinelet. These are probably resorbed and the material used in the next distal plate to be 

 formed. The proximal 6-12 slender inferomarginal plates carry i spinelet, the remainder 

 2. They measure 2-25-2-75 mm. in length and their sheaths contain a few crossed 

 pedicellariae 0-33-0-45 mm. long, and a lanceolate straight pedicellaria 0-5 mm. long. 



The abactinal skeleton of rays is reduced to tiny scattered plates sometimes carrying a 

 tiny spinelet. The antiambulacral bars have 3 or 2 plates proximally and are opposite 

 every fourth or fifth adambulacral. The small inferomarginal elements are slightly 

 separated in the sample examined. 



The papulae of disk and proximal half of ray are in numerous groups of 2 or 3 ; 

 distally they are mostly single. The actinal channel is smooth, soft, and crossed by 

 transverse furrows between inferomarginal plates. 



Along furrow margin, from mouth-plates, is a series of pedunculate straight pedicel- 

 lariae with narrow round-tipped valves; length circa 0-6-0-7 mm. 



In the actinal interradial channel can be seen 2 gonopores. In the interbrachial 

 channel are a few small pedunculate straight pedicellariae. 



Type locality. St. 189. Port Lockroy, Weincke Island, Palmer Archipelago, 70 m., 

 I specimen. 



Remarks. This species, if species it is, belongs to the section of the genus with much 

 reduced marginal plates, wherein the marginal or antiambulacral skeleton consists of a 

 series of spaced transverse bars along the side of ray. In this species there are two or three 

 pieces to each bar, the third, when present, representing an abactinal element. In young 

 examples one would expect to find 5, 6 or even more plates, perhaps connecting up with 

 an incomplete or sketchily outlined abactinal reticulum. 



L. hemiora differs from other species belonging in this group, namely chirophora, 

 lactea, belgicae,jojfrei in lacking differentiated superomarginal pustules, or spines, and in 

 having crossed pedicellariae of one general size. If chirophora has varieties lacking the 

 broad unguiculate straight pedicellariae, the crossed should nevertheless appear in two 

 sizes, namely, o-6~o-9 mm. for the larger and 0-3-0-37 mm. for the smaller. In L. 

 belgicae the two sizes are 0-9-1 -17 and 0-4 mm. In lactea the inferomarginal and lateral 

 crossed pedicellariae measure o-65-073 mm., the dorsal sHghtly less; while the repre- 

 sentatives of the small sort, described as numerous, are only 0-2-0-22 mm. long. The 

 only known specimen of lactea has well-differentiated superomarginal spines. 



When all this is said, the remote possibility remains that hemiora may represent a 

 freakish sort of mutation of the variable perrieri. 



