ORDER III SILICISPONGIAE—LITHISTIDA 49 
Siphonia, Park. (Fig. 56). Fig-, pear-, or apple-shaped, with long or short 
peduncle. Body with deep cloaca, into which arched canals running parallel 
with the periphery, together with numerous fine radial canals, conduct. 
Skeleton composed of smooth-rayed, branching dichotriders. Dermal spicules 

Fig. 58. 
Skeletal element of Jerea 
Quenstedti, Zitt., showing ; , 
branching extremities of Plinthosella squamosa,  Zitt. 

rays. Quadratenkreide; Skeleton magnified SO diameters. 
Linden, near Hanover. 49/;. Senonian ; Ahlten, Hanover. 

Fic. 57. 
Jerea pyriformis, Laimx. 
Greensand; Kelheim, 
Bavaria. 1/5 natural size. 
in the form of mon- 2G 
axons and grapnels. 
Abundant in Middle 
and Upper Cretaceous. 
Hallirhoa,  Lamx. 
Like the preceding, but 
invariably short-stem- 
med. Body pyriform 
and lobate, owing to a 

number of deep con- meee 
Bye { : 
strictions. Cenomanian. Rhagadinia rimosa, Roem. sp. Senonian; Ahlten, Hanover. a, Sponge, 
2/3 natural size; b, Skeleton, 4/; ; c, Lobate disk from dermal layer, 40) ; 
d, Spicule of dermal layer, 49/;. 
Jerea, Lamx. (Fig. 
57). Body pyriform, 
flask-shaped or cylindrical, with truncate or depressed summit, in which a 
number of tube-lke canals, vertical in the central portion but arched in the 
peripheral, terminate. Crossing the latter are finer radial canals. Skeleton 
composed of tetraclons and dichotriders. Common in Middle and Upper 
Cretaceous. 
Polyjerea, From., Astrocladia, Thecosiphonia, Calymmatina, Zitt., Turonia, Mich., 
Plinthosella, Zitt. (Fig. 59). Cretaceous. Discodermia, Boc., Rhacodiscula, Zitt., 
etc. Cretaceous and Tertiary. 
Lthagadinia, Zittel (Fig. 60).  Ear-, plate-, or bowl-shaped, short-stemmed. 
Both surfaces traversed by irregular branching furrows, in which the canal- 
icular ostia are situated. Skeletal elements four-rayed, sometimes uniformly 
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