LOWER CAMBRIAN. 53 
In a letter received from Dr. Nathorst, dated February 19, 1892, he 
says that “‘as to Medusites lindstrémi, it has now been proved with certainty 
that it is a true medusa, a specimen having been found showing the 
impression of the genital hollows.” A pencil sketch accompanied the 
note. More recently a sketch of the specimen was published,’ and I have 
had a copy made, as shown by fig. 1 of Pl. XXX. The mouth is at M, the 
genital hollows at G, G, G, G, and the radiating imprints between the 
latter and the outer margin. 
Among some specimens of this species received from the Geological 
Survey of Sweden, I find one that shows very clearly the casts of four 
hollows in the roof of the gastric cavity; also, as rounded protuberances 
between the four raised angles, the genital sacs, g, g, g, g, of Pl. XXVIII, 
figs. 3a, 3b. The roof hollows are shown in a five-lobed specimen by 
Dr. Linnarsson (loe. cit., fig. 9 of Pl. I). The casts of the genital sacs 
were noted by Messrs. Torell and Linnarsson, and Dr. Nathorst describes 
them in detail. He compares casts that he had made of the lower sur- 
face of Aurelia aurita with the casts from the Lower Cambrian at Lugnas, 
and his illustrations show a remarkable resemblance between them. On 
Pls. XXX and XXXI, I have reproduced photographs of casts in soft 
plaster which I made of the lower surface of Aurelia flavidula, in order to 
furnish the student with the means for a direct comparison of the casts of 
the recent and fossil forms. The cast of the lower side of Aurelia (figs. 2 
and 3 of Pl. XXX) shows the quadripartite pyramid formed by the cast of 
the mouth opening; also the outline of the genital sacs. This may be 
compared with the cast of Medusina costata, fig. 1 of Pl. XXX. The cast 
of the uncompressed genital sacs of the fossil medusa is shown by g, 9, 9. 9, 
of figs. 3a, 3b of Pl. XXVIII. 
Dr. F. Schmidt describes the occurrence of a specimen of this species 
in Esthonia, one of the Baltic provinces of Russia, as follows: 
Up to the present only a single specimen of this form is on hand, which agrees 
perfectly with the specimens from the Eophyton sandstone of Sweden. The specimen 
is five-rayed, and rises into a regular five-sided pyramid with raised, obtuse ribs. 
The lower side is arched, with a flat depression in the middle. It shows most 
agreement with Linnarsson’s F. 8. 
The height of the specimen is 40™™, the largest horizontal diameter 53™™, 
1 Sveriges geologi, af A. G. Nathorst, Stockholm. (No date.) Received by Library of U. S. 
Geological Survey in 1895. 
