92 



FOSSIL MEDUS-E. 



essential part of the raid-field, and the radial and circular furrows as only 

 bounding - it. The zone u is not a velum, but the protuberance (Ausguss) 

 of the umbrella surface. The outer parts are due to the thickness of the 

 disk, which first formed a projection, then a fold. The projection would 

 explain the existence of the furrow p; the fold, partly rilled with mud, that 

 of the ridge s. 



The "rosette" is a branched stomach. In view of this character, this 

 species appears to be related to the craspedote family of the ^Equoridae 

 (iEginia, Cunina, Eurybia), which have 8 broad gastral branches, and also 



Fig. 23.— Medusina deperdita. Reproduced from Dr. Brandt's figure, which he describes as follows: 

 s, a sharp and distinct peripheral ridge, of a circular shape; p, circular furrow; u, ring zone; c, inner furrow; 

 in, depressed mid-held; r, radial extension of the furrow c. The lobes of the rosette are of two sizes, alternately large 

 and small. The larger lobes show slight excavations at their periphery aa if it were the beginning of fission, m is the 

 ccelenteric cavity. The eight lobes of the rosette are only additional pouches of the central cavity, u is the projection 

 of the umbrella disk ; not a velum. 



In order to comprehend the details of the peripheral portions of the impression from their origin, one can perhaps 

 imagine that the umbrella rim was thrown inward (orally), so that it formed first a circular projection and later an out- 

 ward fold. The projection then would explain the existence of the furrow j>, and the fold tilled with ooze the existence of 

 the ridge s. 



lack an oral trunk and tentacles, which appear to be lacking in Acalepha 

 deperdita also. However, the latter can not with certainty be referred to the 

 ^Equoridae, for in the recent form the gastral ramifications are long, not 

 short, and, furthermore, are all equal, while in A. deperdita they are alter- 

 nately large and small. 



