DlCTYOSPONGID^:. 



367 



in the same figure. These may be parts of large pinuli, or still another style 

 of cruciform spicule. Characteristic of this species are the curious pentactins 

 or hexactins with curved arms, which lie scat- 

 tered abundantly among the quadrilles (see 

 figs. 26, 27). Other modifications of the pen- 

 tactin are shown in figs. 28 and 30. Consider- 

 able diversity of form is found among the 

 diactins ; some are elongate, pod-shaped, some 

 stout and bean-shaped, others have a strong 

 single curvature or a double curve. A few 

 fragments have been seen which indicate diac- 



Figure 29. Fragments of echfnate spicules of 



tins with clavate or spherical extremities. phragmodict V a catm/ormu, xm. (j. m. o 

 These are represented in figure 30. The only trace of anchorate spicules 

 observed is a minute form shown in the same figure. 



The elements of the skeleton, taken as a whole, are quite distinct from 

 those of the other species here described. The umbels and clemes, characteriz- 

 ing the genera Piiyso- 



SPONGIA, CLEODICTYA, 



LYKODiCTYA,etc, seem 

 to be wholly wanting. 



Dimejisiona. This 

 species, which is the 

 most abundant of all 

 the forms occurring 

 in the Crawfordsville 

 shales, varies greatly 

 in size. A young and 

 essentially entire in- 

 dividual which prob- 



flVjly rgtainS the pi'O- FIGURE SO. Spicules of Phragmodictya catilliformis, X400. 



Here are shown various forms of dlactlne and cruciform spicules, and among them Is a 

 pOrtlOnS normal for BmaI1 anchorate clavule. (J. M. C.) 



full growth, has a slightly curved cup, its length from the aperture to the 

 distal edge of the periloph measuring 60 mm. The width of its aperture 

 is 50 mm., its median diameter is 28 nun., and its basal width about 25 mm., 

 the periloph having a length of 5 mm. A nearly entire specimen of average 

 size, slightly incomplete at the aperture, has a length of 95 mm., the periloph is 

 15 mm. in length where longest, and the apex of the basal obcone is 9 nun. below 

 the plane of its base. The largest cup observed has an apertural diameter of 



