PLATE XLII. 



Rhizostomites lithographicus (p. 83). 



Fig. 1. Impression of the oral disk. Photograph after the original ; natural size. (After 

 Amnion. ) 

 a-a. Rhombic mid-field. 

 a'. Primary limb of the cruciform mouth seam. 

 a-. Secondary limb of the same (arm seam). 

 y. Apparent bifurcation of the latter. 

 <!]>. Perradial fields of the brachial disk. 

 di I, di II. Interradial areas of the same. 



p. Point of departure of the mouth arms. 

 v aud k. Limestone accretions. 



Rhizostomttes admikandus (p. 76). 



Fig. 2. Impression of portions of two medusa;. One-third life size. (After Brandt. ) 



C. Peduncles or roots of mouth disk. 



D. Base of the peduncles. 



E. Edge of disk. 



F, F\ Peripheral zone of disk (umbrella). 

 G. " Smooth ring." 

 H. Kidney-shaped plates, lids of the genital cavities. 



a. Center of mouth disk and central mouth rudiment. 



b. Primary arms of the mouth cross. 



c. Secondary arms of the same. 



d, e. Isosceles triangles within the mouth cross. 



h. Boundary of the kidney-shaped plates (lids of the genital cavities) and in part of the 



central cavity. 

 i. Oval apertures, entrances to genital cavities. 



A". Circular f nrrow, perhaps indicating the position of the circular canal, 

 s. Boundary of middle field. 

 v, v'. Thickenings of the "smooth ring." 



o. Position of one of the 8 major constrictions which, Haeckel believed, divided the rim 

 into 8 principal lobes. Brandt considers this only a break in the contour, the broken 

 lobes being impressed upon the smaller specimens of R. admirandus, as represented 

 in the figure. 



Medusina staurophora (p. 94). 

 Fig. 3. (After Haeckel. ) See description in text. 

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