74 FOSSIL MEDUSA. 



seems to correspond to that thinnest portion of the disk which lies outside of the geni- 

 tal ring, between it and the disk rim, which is thickened by the reversed marginal lobes. 



Farther inward follows a thinner ring, which I designate a genital ring because 

 I believe that I recognize with certainty sexual organs in it. In a favorable light 

 seven contiguous crescentic facets can be recognized on one-half of the disk within 

 the ring. They are directed with the convex side inward, the concave outward, and 

 seem to repeat the wreath of marginal lobes, which are almost twice as large. Their 

 number, in all probability, amounted to 16, and there seems to be no other possibility 

 than to regard them as sex organs, as they agree exactly in form and position with 

 like organs in other acraspedote medusa-. The great number of these sex organs, 

 together with their continuity and contiguity, may appear remarkable, since the Acras- 

 pedae usually possess only 4 or 8 genital glands. In this particular our medusa draws 

 uearer to the craspedote forms, in which often a continuous ring is formed by a large 

 number of tangent genital organs. In any case this conspicuous circumstance appears 

 sufficiently important, according to the general custom ruling in the systematic study 

 of medusa;, to consider our fossil as a representative of a new family among Acraspedie. 



From the notch between each two genital glands, radially to the corresponding 

 peripheral notch, runs a straight line which can not be otherwise interpreted than as 

 a radial canal. 



In the central circular field, which is inclosed by the genital ring, we would 

 expect to find the mouth and its surrounding mouth arms. However, the visible por- 

 tions of this area are so obscure, and the drawing of their boundary lines is so faint 

 and confused, that we should prefer not to give any definite opinion upon it. The 

 only figures which are somewhat clear are two sausage-shaped mounds lying near each 

 other on the periphery of the central field. In any case, the oral arms must have been 

 quite short, or otherwise one at least would project out over the geuital ring. 



As a resume" we have 8 eyes, 8 bunches of tentacles, 16 genital glands, 16 radial 

 arms, and probably 4 simple oral arms. On the other hand, nothing definite has been 

 determined regarding the form of the mouth, of the stomach, and of the system for 

 procuring food which radiates from it. It is, therefore, not possible to determine 

 sharply the whole generic character of our medusa. This much cau be deduced from 

 the form of the well developed marginal lobes and their sufficiently recognizable struc- 

 ture, that it belongs to that division of the higher medusae which Eschscholtz called 

 Phanerocarpae, and Gegeubaur, Acraspedae. In any case, it must belong to that great 

 group with a simple mouth and 4 (or 8) oral arms which Agassiz assembled together 

 as Seinostoime and compared with Rhizostoma?. 



After a somewhat full comparison with the forms of the Semostomse, 

 Dr. Haeckel concludes with these remarks: 



Under these circumstances we cau not euroll our medusa with the Sthenonidae, 

 which stands the nearest among living medusae, but must regard it as the representa- 

 tive of an especial, extinct semostomous family, which we call Bulithotidae and char- 

 acterize in the following manner : Tentacles grouped in bunches, 8 eyes, disk rim lobed, 

 16 sex glands. 



