178 



DlClYOSPONU ID.E. 



ACLCEODICTTA MARSIPUS, Sp. nOV. 

 Plats lv, Figs. 4, 5; Plate lx, ftas. 3-5 ; Platb lxi, Figs. 1-3; Plate lztiii, Figb. 7, 8. 



Sponge robust, elongate, subcylindrical. Basal obcone, when uncom- 

 pressed, expanding at an angle of about 50 degrees; continuing for not more 

 than one-lifth the length of the cup, whence the surface, with a sharp but not 

 angular bend, becomes abruptly erect in its growth. Near the basal disc the 

 cup is at fii'st broadly constricted, thence upward gradually expands and 

 again narrows to the aperture. Thus the form of the sponge is that of a broad, 

 medially inflated tube resting upon a shallow obcone. 



Reticulum. The vertical and horizontal strands foi-m meshes which are 

 divisible into various sei'ies, though, with the usual preservation of the fossil, 



these differences are obscure. The 

 primary series form quad rules Avhich 

 are about 10 mm. on each side, and 

 these are divided by subordinate 

 series in the usual maimer Over 

 the body of the sponge, both hor- 

 izontal and vertical spicular bauds 

 were pi'oduced into erect reticulat- 

 ing lamellae which form a series of 

 fenestrated areoles. The broadest 

 of these lamellae may have a margin 

 of 5 mm. A single poorly preserved 

 specimen in which a portion of the 

 pyritized skeleton is I'etained shows 

 the presence of very large anchor- 

 ate basalia with broadly divergent, 



FioHRE 33. deme, anchorate clavole >nd stauractlns of AcUxodictya ,^ n ^ i i i 



marsipus, i4oo. (J. M. c.) smooth flukes and convex head. 



There are also great pentactins with curved arms, and clemes with short inter- 

 vals between the acuminate lateral processes. These are forms similar to those 

 occuri'ing in Piiysospongia and Cleodictya. A peculiar pentactin (or tetractin) 

 with short club-shaped ai-ms, a foi-m not observed in other species, occurs 

 here among the jiareuchymalia. A figure is also given of a very small pent- 

 actin with long, straight and simple arms. 



Dimensions. The largest and best preserved example, in which the 

 sjjonge is compressed but essentially entire, has a length of 1 40 mm. ; length 



