36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



lated to the bivalved Ostracoda. From the standpoint of metamorpho- 

 sis the Ascothoracica are of small interest, since whatever modifica- 

 tions some of them do undergo effect principally a simplification of 

 the cypris structure. They are all minute creatures parasitic on 

 Actinozoa and Echinodermata. 



The least modified member of the Ascothoracica is Synagoga niira 

 Norman (fig, 13 A), which lives externally on the black corals 

 Antipathes, clinging to the host by the large antennules. Since Syna- 

 goga has well-developed setigerous legs, however, it appears probable 

 that it can relax its hold and swim from one host to another. The 

 species is known only from a few specimens described by Norman 

 (1913). The head and thorax are enclosed in a large, oval bivalve 

 shell, 4 millimeters in length, provided with strong adductor muscles, 

 but the slender, five-segmented abdomen projects freely from the 

 shell and bears a pair of long uropods. The large antennules ( lAnt) 

 are armed with apical hooks ; the six pairs of thoracic legs bear long 

 setae and are evidently adapted for swimming. The mouth parts as 

 described by Norman are slender piercing organs enclosed in a large 

 conical proboscis (Prb). Of all the Ascothoracica, Synagoga mira 

 alone appears to have no metamorphosis and to have retained the 

 ability to swim ; no other species, therefore, has so good a claim to 

 being a primitive cirriped. 



A related member of the Ascothoracica is described by Okada 

 (1938) as Synagoga meiacrinicola (fig. 13 B). This species has the 

 entire body enclosed in the shell, the abdomen being relatively short, 

 but otherwise it is similar to 6*. mira. Okada finds well-dififerentiated 

 males and females in 5". metacrinicola, the sexes being separate in most 

 of the Ascothoracica, in which the males are much smaller than the 

 females. He reports that Norman's specimens, supposed to be females, 

 are found on reexamination by sections to be males with mature 

 spermatozoa. Okada thus demonstrates that the known examples of 

 Synngoga are adult forms and not larvae of an otherwise unknown 

 species, as some writers had suggested they might be. 



The other Ascothoracica that are parasitic on horny corals appear 

 as small budlike bodies on the coral stems. The shells are of various 

 shapes and in some species are enclosed in a tunic derived from the 

 host. In most of these forms the legs are more or less reduced and 

 lack swimming setae. An ascothoracid described by Heegaard (1951) 

 as Ascothorax bulbosa, found in specimens of an ophiuroid, or brittle 

 starfish, has an oval shell (fig. 13 C), the small males being attached 

 dorsally on the females beneath the cuticle of the latter. The body 



