382 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



A few reduced orthotriaenes occur. Clads and rhabdome all about 

 equal in size, 60-100 jjl long, all straight and cylindrical. 



4. Anatriaene. Abundant in the radial bundles. Cladomes for 

 the most part grouped near the surface, some farther out almost at 

 the surface; a few projecting. Rhabdome 3-4 mm. long, 6 \i thick 

 near cladome, then becoming hair-like. Cladome rather shallow, 

 clads 40-48 [x long. 



5. Protriaene. Present over the general surface in the radial bun- 

 dles, but few in number ; some with cladomes below the surface, some 

 with cladomes projecting. Rhabdome 3.5-4 mm. long, 8-12 u thick 

 near the cladome, somewhat thicker below, and then tapering to a 

 hair-like thickness in the usual way. Clads 50-70 [x long. 



Bundles of the under surface include a considerable number of 

 protriaenes, larger than those of the rest of the body and for the 

 most part projecting. Rhabdome reaching 14 \i in thickness, clads 

 120 [x in length. 



6. Sigmas, about 16 [x long, of the usual shape. Abundant in the 

 dermal membrane, including the general and lower surfaces and the 

 lining of the poriferous pits. Very abundant in the canal walls, but 

 absent or only scantily present in the tissue between the canals. 



Holotype.—Cat. No. 21278, U.S.N.M. 



Dendy, 1905 (p. 97). established this genus for a new form, P. 

 cineriformis, from Ceylon, in which the modified triaenes are ir- 

 regular, and an old form, P. (Tethya) merguiensis (Carter), in 

 which Sollas (1888, p. 16, Tetilla merguiensis) had shown that these 

 spicules were only orthotriaenes with short rhabdome. 



Lindgren, 1898 (p. 328), had already merged Tetilla merguiensis 

 in Tetilla (Stelletta) baeca (Selenka), in which the ectosomal mega- 

 scleres are plagiotriaenes with reduced rhabdome; all four rays 

 usually about equal and straight. 



Thiele, 1900 (p. 39), followed Lindgren in this matter of synon- 

 ymy, and further classed several of Kieschnick's names (1896, 1900) 

 as synonyms of T. baeca — namely, T. ternatensis, T. amboinensis y 

 T. violacea, and T. rubra, the first from Ternate, the others from 

 Amboina. 



Lendenfeld, 1903, adopted the synonymy of T. baeca upheld by 

 Lindgren and Thiele, except that he separated from this species 

 two of Kieschnick's forms, T. amboinensis and T. rubra, which he 

 combined and transferred to Cinaehyra (C. amboinensis). While 

 T. merguiensis is perhaps a synonym of T. baeca, Lendenfeld is 

 justified in retaining T . amboinensis Kieschnick as a distinct species, 

 since it has poriferous pits (Kieschnick, 1900), and these are not 

 definitely recorded for T. baeca. although Dendy, 19216 (p. 21). 

 would interpret the apertures in Selenka's type {Stelletta baeca) as 

 such. Lendenfeld's treatment, at the moment, seems to be the safer. 



