142 CEYLON PEARL OYSTER REPORT. 



from which they taper gradually to a very sharp point at each end ; size fairly 

 uniform, ahout - 028 millim. by 0'002 millim. Very abundant in the thin transparent 

 dermal membrane in the meshes of the dermal skeleton ; also found less frequently in 

 the interior of the sponge. 



R.N. 156; 244 (Ceylon seas). 



Sub-Family : EENTERIN/E. 



Haploscleridae in which the microscleres have entirely disappeared and the skeleton 

 consists of a reticulation of oxeote megascleres with little or no spongin. 

 Tli is sub-family is apparently derived from the Gelliinse by loss of microscleres. 

 Inasmuch, however, as the microscleres constitute the most important guides to the 

 classification of monaxonellid sponges, their total loss may in certain cases leave one 

 in considerable doubt as to the true systematic position of the species concerned. The 

 close relationship of Reniera to Gellius I take to be fully established by the form of 

 the megascleres and by their arrangement. In the genus Halichondria, on the other 

 hand, there appears to me to be less certainty, and the long, slender, slightly curved 

 form and confused arrangement of the oxea suggest a possible origin from some 

 astromonaxonellid genus, such as Coppatias, by loss of the astrose microscleres. It is 

 impossible in the present state of our knowledge to decide this question definitely, 

 but it is quite likely that, as regards the genera Reniera and Halichondria, we are 

 dealing with a case of convergent evolution rather than of close genetic relationship. 



Reniera, Nakdo. 



Renierinae in which the skeleton is composed of a close reticulation of usually single 

 megascleres, each forming one side of a rectangular, triangular or polygonal 

 mesh. Spicules short, oxeote or strongylote, usually united together at the ends 

 only by spongin cement. 



Reniera implexa, Schmidt. 



1868, Reniera implexa, Schmidt (50); 1887, Reniera implexa, Ridley and Dendy (1). 



1 identify with this species a single small specimen consisting of a few irregularly 

 branched tubes, mostly about 5 millims. in diameter and widely open at the end. 

 The surface has a minutely reticulate or porous appearance. The colour (in spirit) is 

 brownish-yellow, and the consistence very soft, compressible and tender. 



The skeleton is a rather irregular, triangular-meshed reticulation, for the most part 

 of single spicules, with occasional loose plurispicular bands feebly developed. 



The spicules are slender, slightly curved oxea, gradually sharp-pointed at each end 

 and measuring up to about 0'13G millim. by 0'004 millim., usually perhaps a 

 little less. 



This species has been recorded from the Adriatic by Schmidt, and from the Azores 

 by Ridley and Dendy (1) and Topsent (62). 



R.N. 201 (Stat. LXIV., south of Modragam Paar, 5 fathoms, March 17, 1902). 



