1236 THE VOYAGE OF H.M.S. CHALLENGER. 



4. Micromelissa microptera, Haeckel. 



Lithomelissa microptera, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 2 ; Abhandl. d. k. Akad. 



d. Wiss. Berlin, 1875, p. 78, Taf. iii. fig. 13. 

 Lithomelissa microptera, Biitschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 539, Taf. xxxiiL 



fig. 26. 



Shell smooth, with distinct collar stricture. Length of the two joints = 4 : 6, breadth = 3 : 5. 

 'Cephalis ovate, with a straight sword-shaped horn of the same length and very small pores, some 

 larger ones above tlie stricture. Thorax little larger, ovate, nearly hyaline, with very few and small 

 scattered pores. From its uppermost part arise three short conical wings, scarcely half as long as the 

 -cephalic horn, little curved and divergent downwards. 



Bimensiom.— Cephalis 0'04 long, 0'03 broad ; thorax 0'06 long, O'Oo broad. 



Habitat. — Fossil in Barbados. 



5. Micromelissa mentricosa^ Haeckel. 



Lithomelissa ventricosa, Ehrenberg, 1875, Abhandl. d. k. AkaJ. d. Wiss. Berlin, p. 78, Taf. iii. 

 fig. 11. 



Shell rough, with slight collar stricture. Length of the two joints = 1 : 7, breadth = 1 : 5. 

 Cephalis small, hemispherical, with a small conical horn of half the length, Thorax ovate, very 

 large, papillate, with irregular, roundish pores. From its basal part arise three short and stout 

 conical wings at great distances, shorter than the cephalis. (A transition-form to Scthoca2)sa.) 



Dimensions. — Cephalis 0-02 long, 0'022 broad; thorax 0'14 long, O-ll broad. 



Habitat.- — Fossil in Barbados. 



Genus 553. Peromelissa,^ Haeckel, 1881, Prodromus, p. 433.. 



Definition. — S ethoperida (vel Dicyrtida triradiata clausa) with three divergent 

 solid lateral wings. Cephalis without horn. 



The genus Peromelissa differs from the preceding ancestral form, Micromelissa^ 

 only in the absence of the cephalic horn, which is lost by reduction. 



1. Peromelissa plialacra, n. sp. (PI. 57, fig. 11). 



Shell smooth, with two joints of nearly equal size and similar ovate form. Cephalis in the 

 upper half hyaline, without pores ; in the lower half with four remote, transverse rows of irregular, 

 roundish pores, decreasing in size towards the hemispherical summit. Thorax with twelve transverse 



' 'Peromelissa = Pouch-bee ; 5r^f«, fitXitjau. 



