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 Aiquoride. 
Under this definition the term Trachymenites loses its applicability to 
this species, and Brandt suggests returning to the original name of Acalepha 
deperdita Beyrich. 
In the table of fossil medusx published in 1880, Haeckel drops Trachy- 
menites and refers the species to the general generic term Medusites. 
MEDUSINA QUADRATA Haeckel. 
Pl. XLV, fig. 1. 
Medusites quadratus Haeckel, 1869. Zeitschr. fiir wiss. Zoologie, Vol. XIX, pp. 553, 
560, Pl. XLII, fig. 4. 
Medusites quadratus Haeckel, 1880. System der Medusen, p. 648. 
Medusites quadratus Ammon, 1886. Abhandl. Math.-phys. Classe Kénigl. bayerischen 
Akad. Wiss., Vol. XV, p. 158. 
The outline of this fossil is not round, as in all other fossil medus, 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 subcireular 
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. 
Tf 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 medus, 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 Thaumatide, and Tiara among 
the Oceanid), while sometimes the circumference of the gelatine disk remains fixed 
in a Shape approaching quadrate.! 
! Zeitschr. fiir wiss. Zoologie, Vol. XTX, 1869, p. 554. 
