44 



The Ohio Journal of Science [Vol. XXI, No. 2, 



5. Lysocystites sculptus (Miller). 



Aethocystites sculptus Miller, N. Am. Geol. Pal., First App., 1892, p. 67.3, Fig. 

 1207; 18th Ann. Rep. Indiana Dep. Geol. Nat. Res., 1894, p. 264, PL 2, Fig. 2. 



The types are preserved in the State Museum at Indianapolis, 

 Indiana, and are supplemented by a well preserved specimen collected 

 by Herrick E. Wilson at the type locality, St. Paul, Indiana; this sup- 

 plementary specimen probably is in the Springer collection, in the 

 U. S. National Museum, at Washington, D. C. All specimens .were 

 found in the upper layers of the Laurel formation. Only the exterior 

 of the thee a is well preserved, and this presents the following 

 -characteristics. 



^Jh^^ 



Fig. 3. Diagram showing arrangement of plates of Lysocystites sculptus 

 (Miller). A composite drawing prepared from both the type and the specimen in 

 the U. S. National Museum; not drawn to scale. 



The basal series consists of three plates. Two of these are broad and 

 are truncated above, evidently representing two plates each. The third 

 plate is angular above. The genus evidently was derived from ancestral 

 forms having five basal plates. 



The second series consists of five plates, of which two are truncated 

 at the base, all being angular at the top. 



Alternating with the plates of the second series are five plates belong- 

 ing to the third series. All of the latter are angular at the base and are 

 medially ribbed. Beneath the anal aperture an elongated oblong plate 

 appears to be inserted on the right side of one of the plates of this third 

 series. The significance of this intercalated plate is not understood. 



In each plate belonging to the second series, distally widening ribs 

 radiate from the center to the upper and the two lower lateral corners, 

 where they connect with corresponding vertical ribs on both the first 

 and third series of plates. In addition, those three plates of the second 

 series which are angular below have a fifth more or less distinct vertical 

 rib connecting in each case with a rib following the sutures between the 

 three basal plates. In the upper and lower quadrants of each plate of 



