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



4. Micromelissa microptera, Haeckel. 



Lithometinsa microptera, Elirenberg, 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. xxxiii. 



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 the 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. 



Dimensions. Cephalis 0'04 long, O03 broad ; thorax 0'06 long, 005 broad. 



Habitat. Fossil in Barbados. 



5. Micromelissa ventricosa-, HaeckeL 



Lithomelissa ventricosa, Ehrenberg, 1875, Abhandl. d. k. Akad. 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 Sdhocapsa.) 



Dimensions. Cephalis O02 long, 0'022 broad ; thorax 014 long, O'll broad. 



Habitat. Fossil in Barbados. 



Genus 553. Peromelissa, 1 Haeckel, 1881, Prodromus, p. 433. 



Definition. Sethoperida (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 phalacra, 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 



1 Peromelusa= : Ponch-\)ee ; 



