JURASSIC. 93 



The characteristic features of the species are as follows: A form with- 

 out an oral trunk and arms, with a round mouth, and likewise 8 round 

 pouches radiating from a central cavity. In all these characters there is 

 seen an agreement with the iEquoridse. 



Under this definition the term Trachymenites loses its applicability to 

 this species, and Brandt suggests returning to the original name of Acalepha 

 d&perdita Beyrich. 



In the table of fossil medusa? published in 1880, Haeckel drops Trachy- 

 menites and refers the species to the general generic term Medusites. 



Medusina quadrata Haeckel. 

 PI. XLV, fig. 1. 



Medusites quadratus Haeckel, 1809. Zeitschr. fur wiss. Zoologie, Vol. XIX, pp. 553, 



560, PI. XLII, fig. 4. 

 Medusites quadratus Haeckel, 1S80. System der Medusen, p. (Us. 

 Medusites quadratus Ammou, 1886. Abliaudl. Math.-phys. Classe Kiinigl. bayerischeu 



Akad. Wiss., Vol. XV, p. 158. 



The outline of this fossil is not round, as in all other fossil rnedusa?, but forms a 

 square with rounded corners. The body is surrounded by a very thick ring which, 

 especially in the middle of each side, rolls up into a strong mound. This subcircular 

 marginal mound shuts in a quadratic field of about 52""" on a side. This is split up 

 into four smaller areas, which, however, can be seen only in a favorable light. At 

 least one can discern two faintly defined mounds which run parallel to the four sides 

 of the square disk, meeting in the middle at right angles. 



If one dared hazard an opinion upon the very indistinct and obscure markings of 

 the impression, the four legs of the central cross (r) would appear to indicate four 

 radial canals, which radiated from the four corners of the central stomach. The 

 circular furrow which connects their external ends would represent the rim canal, and 

 the strong elevation surrounding it the thickness of the gelatinous disk. From the 

 form relations, even if they are correctly interpreted, no conclusion can be drawn as to 

 the systematic position of the medusa. Even the square outline discloses nothing 

 definite; for under certain circumstances living medusa?, even of very different fami- 

 lies, take on a quadrate form, owing to a contraction of the radial muscles which 

 accompany the radial canals (Staurophora among the Thaumatida?, and Tiara among 

 the OceanidM'), while sometimes the circumference of the gelatine disk remains fixed 

 in a shape approaching quadrate. 1 



1 Zeitschr. fiir wiss. Zoologie. Vol. XIX. 1869, p. 554. 



