1168 THE VOYAGE OF H.M.S. CHALLENGEE. 



2. Arehiphormis campanulata, n. sp. 



Shell campanulate, with nine prominent denticulate ribs, prolonged into nine terminal feet, 

 which are broad, lamellar, truncate, nearly vertical, one-third as long as the shell. Pores between 

 the ribs circular, disposed in nine longitudinal and seven to eight transverse rows. 



Dimensions. — Shell 0'09 long, Ol broad ; mouth 0-06 broad. 



HaUtat. — Central Pacific, Station 270, depth' 2925 fathoms. 



3. Arehiphormis urceolata, n. sp. (PI. 98, fig. 11). 



Shell urceolate, with nine smooth prominent curved ribs, prolonged into nine triangular 

 convergent short feet, scarcely one-sixth as long as the shell. Pores between the ribs in nine 

 regular longitudinal rows, twice or three times as broad as long, quadrangular, eight to twelve 

 pores in each row. Mouth constricted, half as broad as the shell. 



Dimensions. — Shell 0'13 long. Oil broad; mouth 0'06 broad. 



Habitat. — Central Pacific, Station 266, depth 2750 fathoms. 



Genus 519. Halicalyptra} Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. 

 d. Wiss. Berlin, p. 54 (sensu emendato). 



Definition. — A rchipkormida (vel Monoeyrtida multiradiata aperta) without 

 radial ribs in the wall of the campanulate or ovate shell. Mouth with, a coronet of 

 radial feet. Apex with a horn. 



The genus Halicalyptra and the two following closely allied genera difi"er from the 

 preceding Archiphormida in the absence of radial ribs. The multiradiate structure is 

 indicated only by the terminal spines or feet, forming a coronet around the mouth. 

 These feet are either the free ends of reduced ribs, or new productions of the peristome. 

 Halicalyptra may be derived from Calpophcena and Petalospyris by loss of the basal 

 lattice-plate of the cephalis. But it is also possible that it has been derived from 

 Anthocyrtis by loss of the cephalis, and that its shell corresponds to the thorax of the 

 latter. 



Subgenus 1. Aerocalpis, Haeckel, 1881, Prodromus, p. 427. 



Definition. — Shell smooth, without spines or thorns (other than the feet and the 

 ajiical horn). 



1 iZixHca^Kpira = Sea- veil ; aAj, x.x'Kimr^et. 



