534 
THE VOYAGE OF H.M.S. CHALLENGER. 
Cristellaria, Lamarck. 
Nautilus, pars, Plancus [1739], Linne, Soldani, Walker, Ficbtel and Moll, Maton and Eackett, 
Montagu, Dillwyn, Sower by, Turton, Fleming, Erown. 
Lenticulites, pars, Lamarck [1804], Defrance, Blainville, Nilsson, Hisinger. 
Linthuris, Oreas, Montfort [1808], Defrance, Elainville. 
Phonemus, Pharamum, Anterior, Robulus, Patrocles, Sphincter ulus, Clisiphontes, Uerion, 
Rhinocurus, Macrodites, Pampas, Scortimus, Astacolus, Periples, Montfort [1808]. 
Cristellaria, Lamarck [1816], Defrance, d’Orbigny, Eoemer, Philippi, Eeuss, Czjzek, Cornuel, 
Bornemann, Costa, Egger, Williamson, Parker and Jones, Ivarrer, Carpenter, &c. 
Lenticidina, pars, Lamarck [1822], Defrance, Blainville. 
Polystomella, pars, Lamarck [1822], Blainville, Macgillivray, Thorpe. 
Crepidulina, Defrance [1824], Blainville. 
Saracenaria, Defrance [1824], Blainville, d’Orbigny. 
Planularia, Defrance [1824], d’Orbigny, Munster, Eoemer, Hagenow, Philippi, Karsten, Boll, 
Jones and Parker, Brady, Wright, Blake, Seguenza. 
Robulina, d’Orbigny [1826], Eoemer, Bronn, Michelotti, Eeuss, Czjzek, Bailey, Bornemann, 
Abich, Costa, Egger, Terquem, &e. 
Margimdina, pars, Sowerby [1834] Philippi, Cornuel, Jones, Bornemann, Parker and Jones, 
Brady, Giimbel. 
Frondicularia, pars, Costa [1856]. 
Plemicristellaria, Hemirobulina, Stache [1864], 
The essential features of the Cristellarian shell are the more or less planospiral 
arrangement of the segments and the terminal or periphero-terminal aperture. The test 
always exhibits a certain amount of lateral compression, but this character, as well as the 
extent to which the spiral mode of growth is maintained, varies in different species. In 
the more typical forms, such as Cristellaria rotulata, the shell is of lenticular contour, 
and spiral from beginning to end ; in others, Cristellaria crepidula and Cristellaria 
variabilis for example, it is oval or oblong, and the later segments show a tendency to 
combine in a curved or oblique linear series ; whilst in a few species, like Cristellaria 
tenuis, the helicoid segments are minute and inconspicuous, and the test is scarcely 
distinguishable from that of Vaginulina. 
The convolutions of the shell are sometimes involute, that is to say, each whorl of 
chambers completely invests its predecessor, as in Cristellaria rotulata; sometimes 
evolute, with the whole of the segments visible on' both lateral faces, as in Cristellaria 
siddalliana ; and sometimes of intermediate character, showing a portion only of the 
earlier convolutions, near the centre on either side. 
The form of the peripheral edge often furnishes the most salient morphological 
feature of the shell. In some members of the genus the margin is thick and rounded, in 
others it is angular and sharp, whilst in a certain number it spreads out so as to form a 
delicate lamelliform wing or keel, which is occasionally armed with radiating spines. In 
the partially uncoiled varieties, the ventral face or front aspect of the test also supplies 
distinctive characters of considerable importance, being sometimes very wide, as in 
