324 PORPEMA. 



similar phenomenon in his supposed genus Porpitella, where it merely represents 

 difference in size between tentacles of different ages. Additional evidence that 

 Porpalia is the young of Porpema is afforded by the facts that Haeckel's speci- 

 men of Porpalia was only 4-5 mm. in diameter, and, still more important, that 

 only eight gonozooids appear to have been present. But I can not follow 

 Schneider ('98) in uniting both Porpalia and Porpema with the species with 

 disc-like corm, i. e., Porpita, because as I shall show there are very important 

 structural differences which distinguish them from Porpita. Chun, in his mono- 

 graph of the Siphonophores of the "Plankton" expedition, mentions neither 

 Porpalia or Porpema in text or in synonymy; or even in his list of Atlantic 

 species ('97b, p. 102) including all "bisher aus dem Atlantischen Ocean beschrie- 

 benen und ausreichend charakterisirten Siphonophoren." I have chosen Por- 

 pema, rather than Porpalia, as the name for the compound genus because while 

 both were proposed in the same publication the former was based on the adult, 

 the latter on a young stage. 



Modern authors agree in uniting all Porpitidae with flattened corm in one 

 genus, Porpita. 



PORPEMA Haeckel, 1888. 

 Porpalia Haeckel, 1888. 



Haeckel proposed several specific names under Porpalia and Poi-pema, 

 with neither descriptions nor figures, nor any indication whatever except the 

 localities of capture; a fact which makes systematic revision of the genus 

 difficult. The oldest species which can be referred to Porpema is globosa, of 

 Eschscholtz ('29); his brief description, and figures are amply sufficient for 

 generic and perhaps even for specific identification. Haeckel ('88a) referred 

 P. globosa to Porpalia, and mentioned as a second species P. prunella, from the 

 Pacific, which he shortly after ('88b) described in detail. Under Porpema he 

 mentions ('88a, and '88b) P. lenticula from the Indian Ocean and P. pileata from 

 the coast of Chile by name only, and fully described P. medusa from the Atlantic. 

 Fortunately he clearly designated a type species for Porpalia, in the words 

 ('88b, p. 58) "the genus Porpalia is founded upon a new species, Porpalia 

 prunella " and this is a starting point. 



A comparison of Eschscholtz's ('29) figures of P. globosa and Haeckel's 

 account of P. medusa shows a close agreement between the two; and inasmuch 

 as both were taken in the Tropical Atlantic, I have no hesitation in uniting 

 them. 



