370 



Report of the State Geologist. 



Aci/EODICTYA MABSIPUS, Sp. IIOV. 

 Plate lv, Figs. 4, 5 ; Plate lx, Figs. 3-5 ; Plate lxi, Figs. 1-3 ; Plate lxviii, Figs. 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-fifth 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 first 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 form meshes which are 

 divisible into various series, though, with the usual preservation of the fossil, 



these differences are obscure. The 

 primary series form quadrules which 

 are about 10 mm. on each side, and 

 these are divided by subordinate 

 series in the usual manner Over 

 the body of the sponge, both hor- 

 izontal and vertical spicular bands 

 were produced 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 retained shows 

 the presence of very large anchor- 

 ate basalia with broadly divergent, 

 smooth flukes and convex head. 

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

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

 occurring in Physospongia and Cleodictya. A peculiar pentactin (or tetractin) 

 with short club-shaped arms, a form not observed in other species, occurs 

 here among the parenchymalia. 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 

 sponge is compressed but essentially entire, has a length of 140 mm.; length 



FIGURE 32. Cleme, anchorate clavule and stauractlns of Aclocodictya 

 marsipus, x400. (J. M. C. ) 



