Dec, 1920] Cystids and Blastoids 47 



of Chicago Universit}', for instance, there are five Racine specimens of 

 Lysocystites nodosus, numbered 18943, all casts of the interior, in dif- 

 ferent states of preservation. Using the entire series, practically all 

 the details already described in the case of specimen number 21815 can 

 be made out. They differ from the latter chiefly in the appearance of 

 the two series of nodes (Plate I, Fig. 11 D). These are not cuneate in 

 outline and are not crossed at what corresponds to their truncated ends 

 by a transverse groove. Moreover, these specimens are smaller in size 

 than the one numbered 21815, but in all other features they so closely 

 resemble the latter as evidently to be congeneric. Since there is no 

 question of specimen number 21815 being congeneric with Aethocystites, 

 the specimens numbered 1S943 belong here also. The latter, however, 

 are identical in character with the type of Lysocystites nodosus, so that 

 the latter also evidently is congeneric with Aethocystites. 



Exterior surface. — In the preceding lines it was mentioned that the 

 cast of the interior of Lysocystites nodosus had been found by Arthur 

 W. Slocom forming the interior of a specimen of Aethocystites. At the 

 time of my visit to Chicago, this specimen was not accessible, but another 

 specimen of Aethocystites, presenting the cast of the exterior, found in 

 the Cedarville colomite at Wilmington, Ohio, forms number 2193 of 

 the Walker Museum collection at Chicago University, and evidently 

 has some bearing on the subject since the Cedarville dolomite carries a 

 typical Racine fauna. This cast of the exterior shows the very charac- 

 teristic surface markings of Aethocystites, including the nodes at the 

 four angles of the plates of the second series. Only two plates of the 

 second series are preserved, one of them truncated at the base, the 

 other pointed. The original height of this Wilmington specimen is esti- 

 mated at 19 mm.; the height of the Racine specimen numbered 21815, 

 the first one described here, is about the same, but the specimen appears 

 more rotund. 



Locality and Horizon. — In the type area, Lysocystites 

 nodosus is known definitely only from Racine, Wisconsin. 



Remarks. — It is possible that there are two species of 

 Lysocystites in the Racine dolomite of Wisconsin. In that case, 

 the term Lysocystites nodosus must be restricted to forms like 

 the type, in which the nodes at the four corners of the plates 

 of the second series are not conspicuously cuneate in outline, 

 and do not have their truncated ends similarly separated from 

 the remainder of the nodes by transverse grooves. Specimen 

 21815 possibly belongs to a second species, and the cast of the 

 exterior of Aethocystites, numbered 2193, from Wilmington, 

 Ohio, may not belong to either of these species. For the present, 

 however, all are regarded as belonging to a single species, the 

 term Lysocystites nodosus covering all the forms here discussed. 



