42 AGLAOPHEXIA GRACILIS. 



intrathecal ridge transverse. Supracalycine nematophores stout, slightly 

 overtopping the hydrotheca ; mesial nematophore attaining nearly half 

 the height of the hydrotheca, adnate for nearly its entire length ; two 

 cauline nematophores on each internode of stem, one of which is situated 

 close to the axil of the pinna, and the other near the distal end of 

 the internode. 



Gonosome. — Corbula with about ten pairs of leaflets ; leaflets quite free, 

 narrow, with denticles nearly equally developed on each edge and with 

 a spur-like denticle at its base ; peduncle of corbula carrying a single 

 hydrotlieca. 



Off Sand Key, from a depth of 100 fathoms. 



In its trophosome this species comes very near to Aglaophenin lophocarpa. 

 It differs from it, however, in the occurrence of a slight angular bend be- 

 tween every tw^o internodes of the pinnce, and more especially by its open 

 corbula?. 



There can be little doubt that the open condition of the corbulce is 

 not here the result of an immature state of these bodies. Like a similar 

 condition of the corbulaa of other species, it is of considerable morpho- 

 logical interest as a persistent state of a condition elsewhere transitory. 



The nature of the denticles along the edges of the leaflets is very 

 obvious in this species. They are plainly seen to be nematophores of 

 the ordinary Aglaophenian type. Their cavity communicates by an aper- 

 ture in the base with the interior of the leaflet, and through this 

 aperture their contents become united with the coenosarc of the leaflet. 

 The coenosarc does not uniformly fill the leaflet, but is disposed in the 

 form of a loose, irregular network of intercommunicating channels. 



Aglaophenia gracilis. 

 PL XXV. Figs. 1-4. 



Trophosome. — Ilydrocaulus attaining a height of about three inches, 

 sparingly branched, not ftiscicled ; pinna3 alternate, springing from a point 

 near the distal end of each internode ; internodes of pinnae witli two 

 strong but short septal ridges, one on a level with the short, strong 

 intrathecal ridge, the other on a level with the base of the supracaly- 

 cine nematophore. Hydrotheciii deep, slightly widemng towards the 

 orifice, with strongly toothed margin ; intrathecal ridge strong and short, 



