392 THE VOYAGE OF H.M.S. CHALLENGER. 



five, but may amouut to niiieteeu, to tweuty-one or more ; they lie constantly in pairs 

 on botli sides of the equatorial constriction (PI. 40, figs. 12, 13). 



The cortical shell may either remain simple {Ommatocamj^e, PI. 40, fig. 10), or 

 become double {Desmoccw^ye, PI. 40, fig. 12), or sometimes triple {Zygocampe, 

 (PI. 40, fig. 13). In the latter cases the outer (secondary and tertiary) cortical shells 

 are commonly incomplete, and only developed around the proximal chambers of the 

 complete first (primary) cortical shell, its distal chambers remaining simple. 



The Medullarij Shell is constantly double, as in the Panartida ; its form is either 

 spherical or lenticular, compressed in the direction of the main axis. It is always 

 connected with the ecpiatorial constriction of the cortical shell b}' a number of 

 radial beams, lying either in the ecpiatorial plane or on each side of it (PL 40, 

 figs. 10-13). 



TJie Central Capsule of the Zygartida is constantly cylindrical ; its increasing 

 growth on both poles of the axis corresponds to that of the including cortical shell. 

 Commonly (but not always) its cylindrical surface is annulated, with five or more 

 transverse strictures, corresponding to those of the cortical shell. From the inner 

 surface of the latter it is separated by a jelly-mantle, the calymma. 



Synopsis of the Genera of Zygartida. 



^ _ ., f Without polar tubes, . . . .169. Ommatocampe. 



L Ommacampida. 



1. Cortical shell simp'e. ■, ^yj^jj ^wo hollow fenestrated tubes, on the poles 



(Medullary shell double.) ^ of the axis \10. Ommatarfa,. 



^^ ^ ., r Without polar tubes, . . . .171. Desmocampr. 



II. Desmocatnpida. '^ 



2. Cortical shell double . with two hollow fenestrated tubes, on the poles 



(Medullary shell double.) ^f the axis, .... Xli. Demnartus. 



-.-.-. „ ., f Without polar tubes, . . . .173. Zi/gocampe. 



III. Zygocampida. I ■ > ^ 



3. Cortical shell triple -j ^y.^,^ ^^^^^ \^o\\o^^■ fenestrated tubes, on the 



(Medullary shell double.) ^ poles of the a;eis, .... \U. Zygartus. 



Genus 169. Ommatocamp)e,'^ Ehrenberg, 1860, Monatsber. d. k. preuss. 

 Akad. d. Wiss. Berlin, p. 832. 



Definition. — Zygartida with simple cortical shell and double medullary shell, 

 without polar tubes. 



The genus Ommatocampe was founded by Ehrenberg in 1860 for one of his " Haliom- 

 matina" with, the following diagnosis : — " Shell rod-like, long, articulate, with nucleus, 

 without spines, with four or more joints." The species figured liy him, Ommatocampe 



1 0)n.m<'<oc(())y)C = Caterpillar with eyes; ljf/.fi% y.-ifmr. 



