1086 THE VOYAGE OF H.M.S. CHALLENGER. 



straight, much longer than the thorax, divergent, and at the broader base irregularly fenestrated, 

 without three larger holes. 



Dimensions. — Cephalis 0'05 long, O'OS broad ; thorax 0-07 long, 012 broad. 



Habitat. — North Pacific, Station 241, depth 2300 fathoms. 



3. Acrospyris p)yramidalis, n. sp. 



Shell three-sided pyramidal, with slight collar stricture. Cephalis campanulate, with deep 

 sagittal stricture and stout ring, armed with a strong pyramidal horn of the same length. Thorax 

 shorter and broader, truncate. Pores irregular, roundish, scarce. Three feet divergent, three-sided 

 pyramidal, as long as the cephalis. 



Dimensions. — Cephalis O'Oo long, 0'06 broad ; thorax 0'02 long, 0-08 broad. 



Habitat. — Fossil in Barbados. 



4. Acrospyris macrocephala, n. .sp. 



Shell spinulate, with deep sagittal and very deep collar stricture. Cephalis very large, nut- 

 shaped, twice as long and broad as the small, truncate, pyramidal thorax. Pores irregxdar, roundish. 

 Horn spindle-shaped, nearly as long as the cephalis ; the three divergent feet are of the same form 

 and size as the horn, and arise as three ribs from the deep collar stricture. 



Dimensions. — Cephalis O'l long, 0'15 broad; thorax 0'05 long, 0"09 broad. 



Habitat. — Fossil in Barbados. 



5. Acrospyris fragilis, n. sp. 



Shell very thin-walled and fragile, with deep sagittal and collar strictures. Pores very small 

 and numerous, circular. Cephalis nut-shaped, nearly spherical, with a slender bristle-shaped horn 

 of the same length. Basal stricture with two large collar pores only (luminella). Thorax nearly 

 three-sided prismatic, longer than the cephalis, with three parallel riljs, prolonged into three slender, 

 long, bristle-shaped feet. 



Dimensions. — Cephalis 0'05 long, 0'06 broad ; thorax 0'08 long, 0'06 broad. 



Habitat. — North Pacific, Station 244, surface. 



Genus 475. Phormosjyyris,^ Haeckel, 1881, Prodromus, p. 442 {sensu emendata). 

 Definition. — P h o r m o s p y r i d a with three basal feet, without apical horn. 



The genus Phormospyris has been derived from Acrospyris, its ancestral form, by 

 reduction and loss of the apical horn ; it therefore bears to the latter the same relation 

 that Tristylospyris has to the ancestral Tripospyris. 



1 PAonreo.'ipj/ns = Wicker- basket ; (po^fto;, a-Tru^ii. 



