30 THE MEDUSAE. 



Atorellidae Vanhoffen. 

 This family, founded by Vanhoffen (: 02 a , p. 51) for the new genus 

 Atorella with six rhopalia and six tentacles, occupies an obscure posi- 

 tion among the Coronata. Not only is the number of marginal organs 

 unusual, but the fact that there are only four gonads, and these, as we 

 shall see (p. 32) without any anatomical evidence of a double nature, is 

 remarkable. The number of tentacles and sense organs may readily be 

 derived, either through duplication, a process which has apparently played 

 an important part in the phylogeny of the different genera of the Periphyl- 

 lidae, or by reduction. But the condition of the gonads is less easy to account 

 for. So far as we know, eight is the primitive number of these organs in 

 every other genus of the order ; and although in certain forms, e. g. Palephyra, 

 pairs of adjacent gonads may become secondarily apposed, or even partially 

 united, yet such pairs always show evidence of their double origin. Whether 

 we are to regard the gonads in Atorella as a further step in such a process 

 of fusion, or as the primitive condition for this form, must remain problem- 

 atic until their development can be studied. 



Atorella Vanhoffen, 1902. 



Atorellidae with 1x6 tentacles and with only four gonads. 



The single specimen for which Vanhoffen (: 02") founded the genus was 

 exceedingly fragmentary, allowing of little more than a determination of 

 the number of tentacles and of rhopalia. More recently Maas (: 03, p. 10) has 

 described, from the collections of the " Siboga," a second specimen in abetter 

 state of preservation, which he has identified as Vanhoffen's A. subcjlobosa. 

 Three specimens in the present collection undoubtedly belong to this same 



genus, but differ s arkedly from the "Siboga" specimen in the sculpture 



of the exumbrella, structure of the tentacles, and general form, that I 

 believe tiny belong to a distinct species. 



Atorella vanhbffeni, sp. nov. 

 Plate 1, Fig. 0Type; Plate 1 I. Figs. 1-8; Plate 12, Figs. 2-Jf. 

 Siai inn It; III, surface. Three specimens, one in excellent, the other two 

 in fair, condition. Their dimensions are : — two 5 mm. high and 6 mm. in 

 diameter, the third more flattened, 3 nun. high and 7 mm. in diameter. In 

 all three the ring furrow is deeply marked (PI. 11, fig. i). In A. subglolosa 

 Imili ' inhoffen and Maas describe the exumhrellar surface as smooth. In 



