REPORT ON THE DEEP-SEA MEDUSAE. 



IX 



talia (Anthomedusae, Narcomedusae), and an order with vascular genitalia (Leptomedusae, 

 Traehomedusae). Those differences are clearly shown by the following tables : — 

 § 8. Survey of the two sections of Craspedotae. 



Leptolin/E (Acordylite). 



Craspedota? without auditory clubs or cordyli, with 

 very movable and extensible tentacles, which are 

 usually hollow. 



Trachylin2E (Cordyliotse). 



Craspedotae with auditory clubs or cordyli, with stiff 

 and slightly extensible tentacles, which are usually 

 solid. 



Order I. Anthomedus.e, PI. I. 



(System, p. 3, taf. i.-vii) 



Genitalia gastral (reproductive organs originally in 

 the subumbral wall of the stomach), descent from 

 Tubularia polyps. 



Order IL Leptomedosj;, PI. II. 



(System, p. 3, taf. viii-xv.) 



Genitalia vascular (reproductive organs originally in 

 the subumbral wall of the radial canals), descent 

 from Campanularia polyps. 



Order III. Trachomedus^e, Pis. III. -VIII. 

 (System, p. 234, taf. xvi.-xviii.) 

 Genitalia vascular (reproductive organs originally in 

 the subumbral wall of the radial canals), usually 

 without peronia on the umbrella margin, never 

 with peronial canals. 



Order IV. Narcomedus/E, Pis. IX -XIV. 

 (System, p. 299, taf. xix.-xx.) 

 Genitalia gastral (reproductive organs originally in 

 the subumbral wall of the stomach), peronia on the 

 umbrella margin, usually with developed peronial 

 canals. 



§ 9. Orders of the Acraspedae (System, pp. 362, 449, 632). The section of the 

 Acraspedae or Scyphomedusse is divided into two sub-sections and four orders. The first, 

 older and lower sub-section, the Tesseroniae (or Tetraperiae), has a highly arched, usually 

 conical umbrella, and on its subumbral side four large perradial gastral pouches, separ- 

 ated by four interradial septa or cathamma, in whose subumbral wall the genitalia are 

 developed. The second, younger and higher sub-section, the Ephyroniae (or Octoperiae) 

 has, on the contraiy, a depressed, usually discoid umbrella, and on its subumbral side, a 

 very wide, flat gastral cavity, into which the four original perradial pouches have been 

 merged, and in whose subumbral wall the genitalia are therefore developed ; the four 

 interradial septa or cathamma have undergone retrograde formation, and are mostly lost. 

 A further distinction between the two sub-sections lies in the number of their character- 

 istic sense clubs or rhopalia. All Ephyronia or Discomedusse have eight or more sense 

 clubs (four perradial, four interradial, often several accessory), whilst the Tesseroniae have 

 only four sense clubs, or none at all. Of the three orders of the Tesseroniae, the Pero- 

 medusae have four interradial rhopalia, the Cubomedusae four perradial, and the Stauro- 



(ZOOL. CHALL. EXP. — PART XII. — 1881.) M b 



