1915,] NATURAL SCIENCES OF PHILADELPHIA. 55 



scales similar to those of the disk. Arm joints invisible in the 

 proximal part of the arm, but more or less distinct distally. First 

 tentacle pore free of arm spines; those beyond provided with a single 

 spine, which is very small, short, peg-like, somewhat flattened, 

 rough at the end as seen under a microscope, lying flat on the ventral 

 surface of the arm. Half way out on the arm, each tentacle pore 

 is provided with two spines, of which the second, or abradial one, 

 is exceedingly small and rather inconspicuous; the adradial one 

 then becomes a little longer and erect to the arm. Color in alcohol : 

 white or pale yellow. 



Numerous specimens; Sagami Sea. 



In smaller specimens, the arms are scarcely widened at the base, 

 which is also the case in regenerating ones; for schizogony takes 

 place in this species as in the genotype, A. virgo Koehler. Most 

 specimens are five-armed, but the arms are often unequal, two or 

 three being larger than the others. I have, however, one specimen 

 with six arms, three larger and three smaller. In four-armed speci- 

 mens, two or three arms may be larger and the other two or one 

 smaller. Still another specimen has only three arms, doubtless 

 indicating that it has lately undergone division, and that the lost 

 parts have not been regenerated. 



Family 3. QORGONOCEPHALID^ Doderlein, 1911. 

 (Characters as given in key, p. 46.) 



Key to subfamilies of Gorgonocephalidoe (/) . 



A — Teeth, dental papillae and oral papillse all similar, spiniform; 

 oral angles not strongly projected ventrally; genital slits 

 small, often pore-like, lying near the disk border; basal 

 vertebrae not very small, not covered over by the muscles 

 between the basal vertebrae and genital plates, 



GoRGONOCEPHALINiE. 



.A^^Teeth and dental papillae similar, spiniform; oral papillae 

 absent or, at least, extremely reduced; genital slits large, 

 extending nearly from the inner corners of the interbrachial 

 ventral surfaces to the disk margin; basal vertebrae very 

 small, covered over by the muscles, which connect the basal 

 vertebrae and genital plates Astrotomin^. 



Key to subfamilies of Gorgonocephalidce {II). 



A — Arms simple or branched a few times. 



a — Teeth, dental papillae and oral papillae all well developed; 

 oral and adoral shields in direct contact with each other, 

 without supplementary plates in the oral region, 



GORGONOCEPHALINiE, parS. 



