K. OKIXOSEAXA. — GEN. CHARACTERS. SZo 



37 mm. by o4 mm. in diameter. In general appearance it agrees 

 well with Eupledella marshaUl. Tlie beams are mostly Y^-l mm. 

 wide, the thinner ones being somewhat laterallj' compressed bnt 

 the thicker ones so flattened as to present broader sides exter- 

 nally and internally. In two or three places they join together 

 to form nodal plates 2-4^ mm. in width. Among the beams no 

 radial spoke-like arrangement can be discerned. This is in 

 accordance with the absence, in the sieve-plate border, of such 

 large oxypentactins as are present in other species of tlie genus, 

 which might give rise to a radial arrangement of the beams. 

 The meshes are oval, oblong or angular but always with 

 rounded corners. They measure more usually 1-4'A, mm. across. 

 An interesting fact is that most of the meshes are each provided, 

 like tlie parietal oscula, with a thin, narrow, iris-like membrane 

 that leaves a round aperture in the middle. 



The Cliff is very broad with a wavy edge-line, measuring in 

 places 22 mm. in width, and is irregularh' undulating, being 

 directed obliquely upwards and outwards. It is soft and 

 moderately thick. The free edge bears an inconspicuous row of 

 projecting spicules, not more than half a millimeter in length. 



The ledger are low in a narrow zone directly behind the 

 cuflf; so also in the basal section of the sponge. In the remain- 

 ing major part of the wall, they are very prominently developed 

 in the form of thick, round-edged and extremely irregular ridges, 

 which vary greatly in height at different points. They may in 

 places be 20 mm. high and 4 mm. or more thick. They frequently 

 branch in their course, making it difficult to determine the 

 general direction they take. Here and there are seen evident 



