THE MOUNT DESERT REGION 



89 



Skeleton. The skeleton is consistently unispicular and 

 regularly reticulate with some triangular instead of charac- 

 teristic rectangular meshes. The spicules are bound together 

 at their ends by small masses of spongin. 



Spicules. These are oxea varying in length from .145 mm. 

 to .185 mm., with a modal length of .162 mm. 



Remarks. In skeletal arrangement and size of spicules 

 this specimen closely resembles Chalina oculata, but it has not 

 been considered such because of its obviously encrusting mode 

 of growth, which has never been encountered in C. oculata 

 even in very young forms, and also because of the tendency 

 in the latter species for the spicules to be enclosed in a very 

 thin sheath of spongin, which does not appear to be the case 

 for this specimen. 



Lambe has recorded from the Gulf of St. Lawrence a new 

 species, Reniera rufescens, which has a 'moderately regular' 

 unispicular reticulum of oxea varying from .124 mm. to .189 

 mm. in length. A comparison between Bowerbank's (1874, 

 pi. 48, tigs. 1-5) figures for R. cinerea and those of Lambe 

 (1893, pi. 4, fig. 6) for R. uifescens, shows identically the same 

 habit of growth. In Bowerbank's specimen the spicules meas- 

 ure .152 mm. in length, whereas those in Lambe 's specimens 

 vary in length from .124 mm. to .189 mm. There seems to be 

 no apparent reason for considering Reniera rufescens as dif- 

 ferent from the previously described R. cinerea, especially 

 as the latter is known from Davis Strait, which is one of the 

 places where Lambe has taken R. rufescens but not R. cinerea. 



Geographical distribution. Davis Strait (Lundbeck) ; 

 Mount Desert Eegion. 



Reniera heterofibrosa Lundbeck 



Lundbeck (1902, p. 47, pi. 2, fig. 8; pi. 11, fig. 11). 



This species is an encrusting form which occurs abundantly 

 in this region and outwardly resembles Halichondria panicea 

 very closely, but an examination of the spicules places it 

 without doubt in the genus Reniera. 



