90 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



A curious ampkipod parasite was found partially embedded in the disks of some 

 of these specimens which I gave to Mr. Clarence R. Shoemaker who described them in 

 1919 under the name of Laphystiopsis iridometrae (see part 2, pp. 633, 634). 



In 1922 Dr. T. Gislen in his memoir on the crinoids collected by Dr. Sixten Bock 

 suggested that the examination of more ample material would probably show that 

 Iridometra adrestine and /. melpomene are really identical, and a reexamination of the 

 specimens at hand leaves no doubt in my mind that this supposition is correct as Dr. 

 Gislen himself concluded in 1927. 



Remarks [BY A.M.C.]. In 1918 Mr. A. H. Clark included his own Antedon 

 minuta in the synonymy of adrestine but without comment. In 1922 Gislen challenged 

 this on the grounds of the large number of segments in the much smaller PI of minuta. 

 In spite of this Gislen in 1927 still included minuta in the synonymy of adrestine, while 

 Mr. Clark, at about the same time, appears to have reconsidered, as he maintains 

 minuta as a valid species in the genus Annametra on the grounds of the cirri, the longest 

 segments of which are only a third again as long as wide while in adrestine of similar 

 size (arm length about 30 mm.) they are two to two and a half times as long as wide 

 (Gislen, 1927). 



IRIDOMETRA MAXIMA A. H. Clark 



Iridometra maxima A. H. CLAKK, Journ. Linn. Soc. (Zool.), vol. 36, 1929, p. 635 (listed), pp. 659-660 

 (locality; diagnosis; description), pi. 43, figs. 12, 13; Proc. Biol. Soc. Washington, vol. 47, 1934, 

 p. 10. 



? Iridometra adrestine (not of A. H. Clark) GISLEN, Ark. Zool. vol. 19, No. 32, 1928, p. 10 (Challenger 

 station 219; notes). 



Diagnostic features. A very large and robust species of Iridometra in which the 

 centrodorsal is large and hemispherical, with a deeply concave dorsal pole; the arms 

 are up to 95 mm. long, at which size the cirri are L-LV; PI is 12 mm. long, with 13 or 

 14 segments; P 2 is 13 mm. long, with 13 or 14 segments; and P 3 is from 11 to 14 mm. 

 long, with 15 or 16 segments. 



Description. The centrodorsal is hemispherical, 5 mm. in diameter at the base 

 and 3 mm. high, with a deeply sunken papillose dorsal pole, about 2 mm. in diameter. 

 The cirrus sockets are arranged in four, and a partial fifth, closely crowded, alternating 

 rows, the size of the sockets decreasing gradually from the proximal to the apical rows. 



There are between L and LV cirrus sockets. All the cirri are lost. 



The radials are short, from four to six times as broad as long; their anterolateral 

 angles are separated by a notch. The diameter of the radial ring is slightly less than 

 that of the centrodorsal, so that the latter has a knoblike appearance. The IBr, are 

 short, five or six times as broad as long in the median line, trapezoidal, with the lateral 

 borders converging slightly distally. The IBr 2 (axillaries) are broadly pentagonal, 

 half again as broad as long. The lateral sides are short, shorter than those of the 

 IBrj, and make with these a broadly obtuse angle. The anterior angle is approximately 

 a right angle, and the anterior sides are only slightly concave. 



The 10 arms are about 95 mm. long. The first brachial is short, twice as long 

 exteriorly as interiorly, interiorly united in the proximal half, the distal half of the 

 inner border making with the proximal half a right angle, so that the distal halves of 

 the inner edges of two adjacent first brachials lie in the same straight line. The second 

 brachials are usually nearly twice as large as the first, and are irregularly quadrate in 

 shape. The first syzygial pair (composed of brachials 3 + 4) is wedge-shaped, almost 



