22 U.S. NATIONAL MUSEUM BULLETIN 2 72 



Type species. — By subsequent selection (Annandale, 1911c, for 

 the subgenus Spongilla (Eunapius)) Spongilla carteri Bowerbank, 

 1863. 



Definition. — Megascleres moderately stout to very stout amphioxea 

 or amphistrongyla, usually completely smooth, occasionally strongly 

 spined. 



Microscleres absent. 



Gemmoscleres slender to robust amphioxea or amphistrongyla, 

 usually strongly spined and only slightly curved. 



Gemmules moderately abundant in maturing sponge, comparatively 

 small and often somewhat flattened; either scattered throughout the 

 sponge, single or in coherent groups, or forming distinct pavement 

 layer at the base; typically with a well-developed pneumatic layer 

 consisting of several tiers of large and conspicuously polygonal air 

 spaces resembling plant tissue; this layer often surrounding groups of 

 gemmules or the entire pavement layer; gemmoscleres embedded in 

 this layer strictly tangentially over the gemmules, and in an irregidar 

 manner in the interspaces between gemmules; foramen invariably 

 tubular, at least extending to surface of pneumatic coat; tube straight 

 or strongly curved. 



Sponges usually forming flat cushions, rarely massive, usually 

 without noticeable projections; associations with zoochlorellae rare 

 and consequently coloration usually a drab gray. Consistency ranging 

 from extremely fragile to almost stony hard. 



Widely distributed throughout the world, from the Arctic Circle to 

 cold-temperate regions of the Southern Hemisphere. 



Discussion. — The genus Eunapius Gray, as here redefined, is 

 characterized by the absence of free microscleres from both inner 

 symplasm and dermal membrane, by the large columnar or polygonal 

 air spaces of the gemmular pneumatic coat, and by the strictly 

 tangential arrangement of the gemmoscleres in this layer. Introduced 

 by Gray (1867) with the view to the separation of those spongillids 

 with "areolated" and "reticidated" pneumatic coats from Spongilla 

 Lamarck, its original definition including the presence of ''smooth 

 sponge-spicules" must now be considered as ambiguous and insuffi- 

 cient. Obvious shortcomings are Gray's inclusion of Spongilla pauper- 

 cula (synonymous with S. lacustris) in Eunapius, and his retention 

 of S. lordii (synonymous with E.fragilis) within Lamarck's only genus. 

 Nevertheless, the generic name Eunapius can still be used, and it is 

 to be regretted that by Carter's (1881a) unwarranted rejection of the 

 entire system of Gray, taxonomists once again reverted to the use of 

 the generic name Spongilla for all spongillids with acerate gemmoscleres. 



Eunapius Gray, first restored as a subgenus of Spongilla Lamarck 

 by Annandale (1911c), is herewith elevated to full generic ranlc. It is 



