970 



THE VOYAGE OF H.M.S. CHALLENGER. 



I. Subfamily 



Zygostephanida. 

 Four lateral gates (no 

 basal gate). 



II. Subfamily 



Acanthodesmida. 

 Five large gates (four 

 lateral and one simple 

 basal). 



III. Subfamily 



Eucoronida. 



Six large gates (four 

 lateral and two basal). 



IV. Subfamily 



Trissocyclida. 

 Eight large gates (four - 



upper lateral and four 



lower basal). 



Synopsis of the Genera of Coronida. 



Two meridional rings ~| 



S^^l*-^ gates simple, 

 dicular to one f ,-, , , 



another (no basal | Four lateral 8 ates P artl y latticed ' 

 ring). J 



Two meridional rings ") 



(sagittal and frontal) \ v , . , 



incomplete, both I Four lateral 8 ates 8lm P le ' 



truncated by the [ -, , . 



complete horizontal | Four lateral S ates P artl y latticed ' 



basal ring. J 



Two rings (the sagittal 

 meridional ring and 

 the horizontal basal 

 ring) complete, the 

 frontal meridian 

 ring incomplete. 



Two meridional rings 

 (sagittal and frontal) 

 and the horizontal 

 basal ring complete. - 

 All three complete 

 rings perpendicular 

 to one another. 



Basal ring f Gates simple, . 

 without larger I 

 descending 1 Gates partly lat- 

 feet. [ ticed, 



Basal ring with large, regularly 

 disposed, descending feet. Gates 

 simple, 



414. Zygostephamis. 



415. Zygostephanium. 



416. Coronidium. 



417. Acantkodesmia. 



418. Eucoronis. 



419. Plectocoronis. 



420. Podocoronis. 



Four upper 

 gates larger 



than the 

 four lower. 



Gates simple, . 421. Tristephanium. 



Gates partly lat- 

 ticed, 



{Gates simple, . 

 Gates partly lat- 

 ticed, 



422. Tricydidium. 



423. Trissoeir/MS. 



424. Trissocydus. 



Subfamily 1. ZYGOSTEPHANIDA, Haeckel, 1881, Prodromus, p. 446. 



Definition. C o r o n i d a with four large lateral gates, without basal gate. Skeleton 

 composed of two complete vertical rings, perpendicular one to another the primary 

 sagittal and the secondary frontal ring. 



Genus 414. Zygostephanus, 1 Haeckel, 1862, Monogr. d. Eadiol, p. 268. 



Definition. C o r o n i d a with four large, simple, lateral gates, without basal gate 

 and lattice-work. Skeleton composed of two simple meridional rings, perpendicular to 

 one another. 



The genus Zygostephanus, founded by me in 1862 for the Mediterranean Zygoste- 

 phanus mulleri, is the simplest and most primitive of all the Coronida, and may there- 



1 Zygostephamis Yoked ring ; vyov, 



