SYRINGIDIUM. 



427 



Castracane, D. Capreolus is only a spore of a Chcetoceros, and consequently 

 should be named C/i. Didadia ( Ehr.) Cast. See Castr. " Challenger," p. Si, 

 pi. 19, f. 7. 



I include the Thaumatonema of Greville in the Didadia. 



GENUS 93. SYRINGIDIUM EHR., 1845. 



Frustules elongated, with valves furnished 

 with mucronate horns. Valves usually dis- 

 similar, one of them having only a single and 

 the other two horns or processes. 



The genus includes about a dozen forms ; the 

 S: Awuricanum Bail, represented in the margin (fig. 

 145), is found in a living state in Brazil, at Trinidad, 

 and in Bengal, and is also found in a fossil state in 

 Fig, i^.Syringidium the deposit of Nankoori. 



Americanum 



Syndendrium Ehr., 1845. 



Valves dissimilar, one smooth, 

 the other furnished with numerous 

 elongated spines, often ramous. 



According to Mr. Cleve and Count 



Castracane, Syndendrium are only 



Fig. 146. Syndendrium Diadema. spores of Chaztoceros. 



Syndendrium Diadema Ehr., represented in the margin (fig. 146), is found 



in Peruvian <manos. Mr. Lagerstedt has also noticed it at Fiskebackii, 



Bahnsie, and Mr. Norman in Ascidinus off Hull, England. 



GENUS 94. HERCOTHECA EHR., 1844. 



Frustule with dissimilar valves, 

 one slightly inflated with a rounded 

 inflation, the other with a very strong 

 elevation, subconical. Valves bor- 

 dered with a marginal corona of 

 spines or erect needles. 



I give in the margin, after Ehren- 

 berg, Hercotheca ma miliar is Ehr., 



Fig. 147. Hercotheca 

 mamillaris. 



which is found in a fossil state at the Bermudas. 



