SPONGES. 249 



they are likewise gone in the interior of the mass of the illustrated 

 example (PI. Ill, fig. 2a). At the surface, however, the spicules 

 themselves are preserved. 



Position and locality: Rare in the cherty layers of the Bur- 

 lington limestone, at Burlington, Iowa, and Montezuma, Pike 

 county, Illinois. 



From the shales of the Keokuk group I have collected speci- 

 mens of two additional Monactinellid or possible Hexactinellid 

 sponges, which, however, are generic-ally distinct from Belemno- 

 spongia faxcicularis. One is composed of extremely fine parallel 

 fibres, or spicules, the length of which could not be determined. 

 The other, as it is not uncommon, and easily recognized, I pro- 

 pose to name Lasiocladia hindei. A brief description is as 

 follows : 



LASIOCLADIA HINDEI, n. sp. 



Sponge skeleton composed of elongate, slender, straight, 

 acerate spicules, pointed at both ends, and closely arranged 

 in sub-parallel series; their size is generally quite uniform, and 

 varies little from 6 or 7 mm. in length, by 0.12 mm. in diameter. 



The broken spicules of this species, are frequently seen scat- 

 tered over the surface of slabs between the fronds of Fenestella 

 and other bryozoa. A small slab, about two and one-half inches 

 square and more than one-half inch thick, from Nauvoo, Illi- 

 nois, is almost entirely composed of them. In this condition 

 they present no recognizable arrangement, and only one speci- 

 men has been observed in which their normal arrangement is 

 preserved. This is a very thin elongate fragment about 35 

 mm. long, by 7 or 8 mm. in width, which, under the ordinary 

 pocket lens, presents the appearance of being composed of long- 

 itudinal fibr 



The type of the genus (L. compmssa Hiude, from the Lower 

 Devonian of Belgium) differs from L. hindei, in having stouter 

 and shorter spicules. They are also differently arranged, in 

 being directed upward and outward, instead of in longitudinal 

 series. 



31 



