134 THE MEDUSAE. 



The general aspect of this species is shown in the photograph (PI. 2, fig. 

 5), and its color in Vanhdffen's beautiful figure (: 02'', taf. 9, fig. i). I was 

 unable to find any octocysts ; and as I, like Vanhoffen, examined excellent 

 specimens in the fresh condition, with negative results, and since neither 

 Maas nor Browne were able to find any otocysts on preserved specimens, 

 it is probable that this genus actually lacks these organs. The specimens 

 corroborate Maas's (: 05) statement that in the formation of the tentacles the 

 perradial appear first, then the adradial, and finally the irderradial ; indeed 

 even in large specimens the latter remain much the smallest (PI. 45, fig. 12). 

 This type of succession is so unusual that it may well be considered of 

 generic significance. 



This species has a more brilliant iridescence than any other Medusa with 

 which I am acquainted. 



Colobonevia sericeum is undoubtedly an intermediate form. It is one of the 

 few species which have been taken in closing nets, a single specimen being 

 recorded by Vanhoffen (: 02'') from the " Valdivia" collection, from 820-500 

 fathoms. Its geographic range, so far as yet known, includes the north 

 Atlantic (Bay of Biscay, Browne) ; the Tropical Atlantic ; the south Atlantic 

 to 42° S. Lat. ; the Indian Ocean (Vanhoffen); the Malay Archipelago 

 (Maas); and the Eastern Tropical Pacific. 



Pectyllidae Haeckel, 1879. 



Trachomedusae with numerous tentacles arranged in several rows; with 

 well-developed manubrium. 



Only one member of this family, a species of the little-known genus 

 Crossota, is represented in the collection. 



CrOSSOta Vanhoffen, 1902. 



Pectyllidae with numerous tentacles arranged in several continuous hori- 

 zontal rows, but not in groups ; gonads borne on the upper umbrella portion 

 of the radial canals ; without mesenteries. 



This definition is essentially that given by Maas (: 06'^), who follows Van- 

 hoffen in pointing out the close resemblance of this genus to Pectyllis and 

 Pectis. It is, however, simpler than either, being easily distinguished from 

 them by the absence of mesenteries, as well as by showing no trace of a 

 radial grouping of the tentacles. The genus has so far been recorded only 

 from the collections of the " Valdivia " Expedition and from Norway. 



