20r> T. A. STKPHENSON 



absent in the second. Sphincitoi' weak to moderate, more diffuse to more 

 circumscribed. Radial muscle of disc ectodermal. Retractors diffuse 

 or more like circumscribed diffuse, numerous mesenteries perfect. 

 gonads chiefly on stronger imperfects, or on the older mesenteries save 

 sometimes the directives. 

 Species : 



T. aster, Leuck. in Riippel, 1828, p. ">. (See Carlgren, 1900, 



p. 87.) 

 T. kraepelini, Carlgr., inOO, p. 91. 

 T. senckenbergian us, Kwiet.. 1897, p. 337. 

 T. hemprichi, F^hr., 1834, p. 42. (See Carlgren, 1900, p. 94; 



Haddon, 1898, p. 485.) 

 T. hypnoides. Saville Kent, 1893, p. 148. (See Haddon. 1898, 

 p. 48G.) 



1 liiivc joined Tlialassiantlins and Heterodactyla 

 because 1 cannot find any really important differences between 

 them. The definition given covers both, "j'he presence of 

 several siphonoirlyphes in some species, and no directives, 

 of two siphonoglyphes and two pairs of directives in others, 

 seems no valid ground of separation. 



Cryptodendron, Khmz., 1877. 



Thalassianthidae with or without suckers on upper part of body, 

 and with somewhat crenulated margin. Wide irregularly-folded disc. 

 Three sets of tentacles : (n) a set of short exocoelic marginal dendrites ; 

 (b) radial rows of short, simple, and dendritic tentacles on the inner part 

 of the disc ; and (c) an intermediate zone of nematospheres. Sphincter 

 weak to moderate, circumscribed. Well-developed diffuse retractors. 

 The nematospheres especially have apical batteries of sting-cells and 

 glandular stems. Radial musculature of disc and tentacles ectodermal. 

 The nematospheres are in sessile packets, and they and the discal 

 dendrites are endocoelic. 



Species : 



C . a d h a e s i V u m , Klunz.. 1877. p. 86. (See Haddon, 1898. p. 483, 

 and KAvietniewski, 1896.) 



AcTiNERiA, Blainv., 1S80. 



Thalassianthidae A\'ith vertical rows of verrucae in upper part of 

 column, parapet notched a little. Wide folded disc, bare in the middle, 

 with small permanent lobes at the edge. Exocoels ^\ath dendritic 

 tentacles, endocoelic lobes with dendrites (which run inwards on the 

 disc) on the oral side and a mass of nematospheres aborally. Sphincter 



