RHYNCHOLAMPAS. 105 



The genera Palaeolampas, Echinolampas, and Conolampas have been the 

 cause of much discussion. Doubt has been cast on the validity of Conolampas 

 but it is a well-marked group. On the other hand, I have not been able to draw 

 a satisfactory line between Palaeolampas and Echinolampas and have there- 

 fore abandoned the former genus. The genera which seem to be valid for Recent 

 Nucleolitidae may be distinguished as follows. 



Key to the Genera of Nucleolitidae. 



Periproct in a more or less evident depression or groove, usually above ambitus. 

 Apical portion of test not modified to form a sunken brood-pouch. 

 Ambulacra more or less petaloid aborally. 



Transverse diameter of periproct distinctly greater than longitudinal . Rhyncholampas. 

 Transverse diameter of periproct not greater than longitudinal. 



Vertical diameter (v. d.) of test half horizontal diameter (h. d.) or 



less; periproct longer than wide Oligopodia. 



V. d. three fourths h. d. or more; periproct more or less circular . Hypselolampas. 

 Ambulacra not at all petaloid. 



Periproct well above ambitus in a deep furrow Aphanopora. 



Periproct at or below ambitus in a slight depression or somewhat 



overhung by test Neolampas. 



Apical portion of test modified to form a sunken brood-pouch Anochanus. 



Periproct at or below ambitus, not in a groove or depression but flush with surface 

 of test. 



Longitudinal diameter of test greater than transverse; mouth anterior; anterior 



ambulacrum abactinally generally quite different from the others .... Echinolampas. 

 Longitudinal diameter of test scarcely exceeds transverse, so ambitus appears 

 circular; mouth central or slightly posterior; anterior ambulacrum not dis- 

 tinguishable from the others abactinally Conolampas. 



Rhyncholampas. 



A. Agassiz, 1869. Bull. M. C. Z., 1, p. 270. 

 Type, Cassidulus cariboearum Lamarck, 1801. Syst. Anim. sans Vert., p. 349. 



Not long after establishing this genus, Mr. Agassiz abandoned it (1873. 

 Rev. Ech., pt. 3, p. 553) on the ground that "D'Orbigny established the genus 

 Rhynchopygus for Cassidulus guadeloupensis, a tertiary fossil from Guadeloupe, 

 which is probably identical with the species now living in the West Indies and 

 Straits of Florida." As this living species had been virtually designated by Mr. 

 Agassiz the type of Rhyncholampas, he naturally regarded his proposed genus 

 as a synonym of D'Orbigny's. But the fact is, as stated by Mr. Agassiz in 1869, 

 D'Orbigny did not establish Rhynchopygus for Cassidulus guadeloupensis but for 





