130 The Mastigophora 



Lyramula Hanna and Vallacerta Hanna (Fig. 4. 9, E) seem to be limited 

 to fossils from the Upper Cretaceous (101), while Dictyocha Ehrenberg 

 (Fig. 4. 9, AD, F-I) includes both living and fossil types. According to 

 Deflandre (63), three generic names — Cannophilus, Distephanus, and 

 Mesocena — have been applied to forms which fall within the genus 

 Dictyocha. 



Suborder 3. Coccolithina. These flagellates occur mostly in salt and 

 brackish water; only a few are known from fresh water (46). Collections 

 in the Mediterranean (186) have yielded specimens from depths of 400 

 meters, but the flagellates are most abundant in the zone above 100 

 meters. Two flagella of equal length have been observed most frequently. 

 However, a few supposedly uniflagellate types have been reported; also 

 flagella have not yet been seen in some described species. Either two or 

 four chromatophores may be present (179). Little is known about the 

 life-cycles. Schiller (250) has noted in two species of Calyptrosphaera 

 stages which suggest fission within the theca, and he has pointed out 

 the need for study of the Coccolithina in cultures. 



The diagnostic feature of the group is the possession of calcareous 

 coccoUths which may be deposited at the surface of, or embedded within, 

 a secreted membrane (Fig. 4. 2, K). Several types of coccoliths (186, 250) 

 are known. Solid platelets (discoliths), with or without spines, are found 

 in Syracosphaera (Fig. 4. 10, I), Pontosphaera, and related genera. Per- 

 forated coccoliths {tremaliths) are of various kinds. Elongated trema- 

 liths containing a long canal are known as rhabdoUths (Fig. 4. 10, A, B), 

 while simple perforated plates or double discs joined by a short canal 

 are called placoliths (Fig. 4. 10, D). Structme of the coccoliths has been 

 used as a basis for differentiating several families (127). 



Representative genera include Acantltoica Lohinann (46, 250), Calyptrosphaera Loh- 

 mann (250), Coccolithus Schwarz (Fig. 4. 10, F), Deutschlandia Lohmann (250), Dis- 

 cosphaera Haeckel (250; Fig. 4. 10, A), Halopappus Lohmann (250), Hymenomonas 

 Stein (127, 174; Fig. 4. 10, G), Pontosphaera Lohmann (186, 260), Rhabciosphaera 

 Haeckel (250; Fig. 4. 10, C), Syracosphaera Lohmann (31, 186, 250), and Umbilicosphaera 

 Lohmann (186). 



It is uncertain whether Hymenomonas actually belongs in this group. A pitted "shell" 

 has been reported in H. roseola Stein (174), although discrete coccoliths have been 

 described in H. dariubiensis (127). 



Suborder 4. Rhizochrysodina. The amoeboid phase is dominant. In 

 the Rhizochrysidae, the amoeboid stages are solitary or else form loose 

 aggregates with pseudopodial attachments. Genera which develop true 

 Plasmodia are placed in the Myxochrysidae. 



Family 1. Rhizochrysidae. Net-like aggregates of naked organisms (221) 

 are produced in Rhizochrysis Pascher (Fig. 4. 11, E) Chrysarachnion 

 Pascher (Fig. 4. 11, G), and the apochlorotic Lenkapsis Pascher. Similar 

 aggregates of thecate organisms (221) are formed in Heliapsis Pascher 



