ASTEROIDEA 247 



Lysasterias heteractis sp.nov. 

 (Fig. L, 4-46; Plate XX, fig. i) 



Diagnosis. Resembling a specimen of L. perrieri having 8 slender rays. R 87 mm., 

 r 20 mm., br 16 mm., R = 4r plus. 



Description. Abactinal surface with very numerous small pustules of unequal size, 

 enclosing a delicate terete spinelet and 2 or 3 small crossed pedicellariae, or the latter 

 only. These pustules are irregular in outline and separated by narrow grooves except on 

 central area of disk where they are spaced, and the puffy skin can be seen between them. 

 Numerous small papulae, most conspicuous in the interbrachial channels. Spinelets 

 range from i to 17 mm. long by 0-25 mm. thick at base, and the tip is minutely thorny. 

 The pedicellariae are 0-45-0-55 mm. long, the tip broad and bluntly rounded. In 

 profile the outside of terminal lip is long. 



The abactinal skeleton is represented by irregularly and widely scattered separate 

 small plates, or sinuous lines of them suggesting a degenerate reticulation. On side of 

 ray the marginal plates (plus i or 2 small abactinals proximally) form weak oblique 

 costae opposite, on an average, every fourth ambulacral. The inferomarginals touch 

 one another proximally but are separated distally. The superomarginals are transversely 

 elongate and do not touch one another. 



On sides of ray are 2 series of much larger marginal pustules. Superomarginal spine- 

 lets (2-5-3 -5 mm.) abruptly longer than abactinal, generally i to a pustule but occasion- 

 ally 2 at base of ray, and surrounded by about 5 crossed pedicellariae larger than the 

 abactinal (o-75-o-85 mm.). Inferomarginal spinelets slightly thicker than supero- 

 marginal, 2 at base of ray and 1 on outer half or two-thirds, accompanied by 5-8 crossed 

 pedicellariae similar to the superomarginal. Sometimes each proximal inferomarginal 

 spine is surrounded by its own pustule so that there are three in a vertical series. There 

 are a very few inconspicuous small lanceolate marginal pedicellariae. 



The adambulacral spines are slender, rather long (3-3-5 mm.), close-set, and one to 

 a plate. The narrow space between them and the inferomarginal spines is devoid of 

 papulae although intermarginal papulae are present. The swollen inferomarginal 

 pustules usually abut on the upright adambulacral spines. 



The mouth angle is constricted, about 4 pairs of adambulacrals behind the oral plates 

 being in contact. The small oral plates have 4 spines on the actinostomial border of each 

 angle, and close behind these a pair of longer suborals exactly like the following adam- 

 bulacrals. On the mouth-plate and along the furrow face of the adambulacrals are simple 

 lanceolate straight pedicellariae (sometimes with one valve tip hooked over the other) 

 averaging 0-7 mm. long by 0-38 mm. broad at base. 



The madreporite is circular, 3-5 mm. in diameter, and situated at mid-r. 



The ambulacral furrow is wide, the tube-feet numerous and crowded. One can some- 

 times count 5 in a transverse series. 



The gonads (testes) are attached to the interbrachial septum 5 mm. from the inter- 

 brachial sulcus on a level with the intermarginal line. The duct opens at the tip of 



23-2 



