1915.] NATURAL SCIENCES OF PHILADELPHIA. 91 



semicircular, about one-half as large as the dorsal arm plate, and 

 bounded along the distal border by one or two very insignificant 

 secondary supplementary plates, which, however, are present only 

 for a comparatively short distance near the arm base; two or three 

 first dorsal arm plates and their supplementary plates are smaller 

 than those beyond; supplementary plates smaller outwards as 

 dorsal arm plates become quadrangular, and finally disappear. 

 Lateral arm plates not very prominent, meeting neither above nor 

 below. First ventral arm plate very small, rather pentagonal, 

 longer than wide; those beyond, quadrangular, with rounded outer 

 lateral angles, truncated inner lateral angles and slightly notched 

 outer border, nearly as long as wide, but longer than wide distally. 

 Three arm spines, short, stout, flattened, blunt. One large, oval 

 tentacle scale to each pore. Color in alcohol: grayish yellow; disk 

 reticulated, and arms banded, with dark purplish brown. 



Three specimens; Enoshima. Numerous specimens; Aral Beach, 

 Misaki Marine Biological Station.. 



The arm length varies from six to eight times the disk diameter. 

 In smaller specimens the arm spines are less flattened; and in those 

 smaller than 4 mm. across the disk the secondary supplementary 

 dorsal arm plates are 'almost invisible. 



This species differs from the genotype, 0. dictydisca H. L. Clark, 

 in the shape of the dorsal arm plates, in the less distinct secondary 

 supplementary dorsal arm plates and in the smaller and more insig- 

 nificant radial shields. Further, schizogonic reproduction has not 

 been observed in the present species, though I have examined many 

 very small specimens. 0. marklanneri, as well as the genotype, 

 resembles Ophionereis dubia in lacking the genital papillae, but 

 differs from it chiefly in the presence of the secondary supplementary 

 dorsal arm plates and in the much narrower arms. 0. marktanneri 

 is by no means near Ophionereis porrecta Lyman. I could mention 

 some more differences than those enumerated by Koehler between 

 these two species, but it is not necessary to do so here. 



This charmingly handsome species is one of the most common 

 ophiurans about Misaki, living under stones and rocks. 



Family 5. OPHIOCOMIDiE Ljungman, 1867. 

 (Characters as given in keys, pp. 74 and 75.) 



Key to subfamilies of Ophiocomidce. 



A — Radial shields long and wide, boot-shaped, widely separated 

 from each other; three to five arm spines; tentacle scales 

 short and leaf-like Ophiocoaiin^. 



