138 U.S. NATIONAL MUSEUM BULLETIN 2 72 



Color in life. — ^Light gray to light brown. 



Discussion. — The inclusion of this species in the genus Tubella 

 Carter by earlier authors was aided by the rudimentary development 

 of the upper rotule of the great majority of its gemmoscleres. However, 

 Annandale (1911c) realized that this ecomorphic condition represents 

 a convergence of characters comparable to but not identical with 

 that found in Tubella species and relegated T. pennsylvanica to its 

 proper position within the genus Trochospongilla. The species discussed 

 merely represents one extreme of an intergrading series of species, 

 almost all of which display some degree of size differences between 

 their upper and lower gemmosclere rotules. It cannot possibly be 

 left in Tubella, relegated to a synonym of Metania in this paper, 

 since all true members of this genus possess free microscleres, a vastly 

 different construction of their skeleton and gemmules, and gem- 

 moscleres with clearly distinct rotules, in size as well as in structure. 



All the specific and varietal names listed above must be considered 

 fully synonymous with T. pennsylvanica for reasons mentioned in 

 the discussion of T. horrida. Only when comparing a full range of speci- 

 mens from distant localities, as was possible during the present 

 studies, the futility of establishing clear-cut races within T. pennsyl- 

 vanica becomes obvious. 



Trochospongilla leidii (Bowerbank, 1863) 



Plate 12, figures 7, 8 



Spongilla leidii Bowerbank, 1863, p. 445. 



Ephydatia leidyi Gray, 1867, p. 550. 



Meyenia leidii Carter, 1881a, p. 91. 



Meyenia leidyi Potts, 1884a, p. 184; 1887, p. 212.— Kellicott, 1891, p. 103; 1897, 



p. 50.— Kirsch, 1909, p. 37. 

 Trochospongilla leidyi Weltner, 1895, p. 114. — Annandale, 1909d, p. 404. — 



Smith, 1921, p. 17.— Gee, 1926a, p. 181; 1931e, p. 41; 1932b, p. 16; 1932c, 



p. 43.— Old, 1936b, p. 11.— Eshleman, 1950, p. 44. 

 Trochospongilla leidii Penney, 1960, p. 56. 



Material.— Slides of type (BM) and of Pott's material (USNM 

 no. 8639). 



Description. — Sponge, according to the original descriptions by 

 Bowerbank (1863) and Potts (1887), forming thin encrusting layers 

 of considerable dimensions; surface even, sometimes rising into round 

 eminences. Skeleton a rather firm network of more or less regular 

 spicule fibers, forming polyhedral meshes. Consistency of live sponge 

 very hard and firm. 



Megascleres straight to feebly curved stout amphioxea, broadly 

 fusiform and entirely smooth; length range 150-170 n, width range 

 8-13 /z. 



Microscleres absent. 



