312 A. EARLAXD ON CYMBALOPORA BULLOIDES 



of structure hitherto unnoticed, which, in his opinion, necessitated 

 the separation of the species from its congeners, and its removal 

 into a new sub-genus, for which he proposed the name Tretom- 

 phalus. His description of the species, which I will quote in full, 

 is as follows : — 



Tretomphahts hulloides d'Orb. 



(From rprjTo^ pierced, and 6/x^aXo9 navel, or boss of a shield.) 



" The shell consLsts of sharply curved concavo-convex chambers, 

 which are spirally arranged in three coils. The chambers of the 

 last convolution are much more voluminous than the preceding 

 ones. The final chamber especially is very large, and at the 

 base* studded with hemispherical perforated bosses,+ and in 

 the plane of the bosses is furnished Avith a tube projecting into 

 its interior. The greater part of the final chamber is, like all the 

 rest of the chambers, covered with fine 'pore canals.' These 

 have a diameter of •004 mm. The diameter of the bosses 

 amounts to '014 mm., the diameter of their perforations to 

 •008 mm. The whole shell has a length of "265 mm. and a 

 breadth of '20 — -22 mm. 



D'Orbigny described these remarkable forams under the name 

 Rosalina hulloides in " For. Cuba," 1839. He did not know of 

 the existence of the tube in the last chamber. 



W. B. Carpenter placed R. hulloides d'Orb. in the genus 

 Cymbalopora (Hagenow). The characteristic features of this 

 genus are as follows : The chambers have their principal 

 opening directed into a deep oral depression, and they possess 

 side openings as well as a principal opening. These peculiarities 

 are entirely wanting in Rosalina hulloides, for its chambers com- 

 municate with one another through wide openings. I therefore 

 consider it desirable to institute a new genus for these forms, 

 which in my opinion have the following distinctive features : — 



Shell spirally coiled without umbilical depression. | At the 

 distal end of the final chamber are perforated bosses, the rest of 

 the shell has the usual pseudopodial perforations. A tube pro- 

 jects into the interior of the final chamber from the plane of 

 the perforated bosses. 



♦ Literally " at the opposite pole to the primordial chamber." 



t These are the " numerous large ' orbuline ' lipped pores " of Carpenter. 



X Lit. mouth-navel. 



