PALAEOTROPUS. 151 



lariae, seem to warrant its recognition. The smaller of the two specimens is 

 10 mm. long by 8 mm. wide and a trifle more than 5 mm. high but the form of 

 the test is like that of the holotype. 



Station 2922. Off southern California. Bott. tump. 57.1°. 47 fms. 

 Fne. gy. s. 



Two specimens. 



Palaeotropus. 



Loven, 1872. Ofv. Vet. Akad. Forh. f. 1871, no. 8, p. 21. 

 Type, Palaeotropus josephinae Loven, 1872. hoc. cit. 



As already stated (p. 138) the genera Palaeobrissus and Paleotrema are 

 based on growth-stages of Palaeotropus, as I have determined from the study 

 of the material in the M. C. Z. Palaeotropus is a small genus of four, or pos- 

 sibly only three, species, easily recognized by the totally apetaloid nature of 

 the abactinal ambulacra, associated with a well-marked nearly circular sub- 

 anal fasciole and no other. Pedicellariae are numerous and varied, all five 

 forms having been found within the genus, but they are of little taxonomic 

 value, though now and then they furnish good characters. The species are 

 distinguished by the form of the test, the position of the periproct, the shape of 

 the peristome, and the number of genital pores. This last character is of very 

 doubtful value for as will be seen under P. josephinae (p. 152), sexual maturity 

 is attained slowly in Palaeotropus and apparently grown specimens may not 

 have the normal number of genital pores. 



Key to the Species of Palaeotropus. 



Test highest posteriorly; subanal fasciole, when present, not longer than wide; periproct 

 at or above posterior margin of test. 



Test not narrower in front than behind. 



Peristome 1.5-3 times as wide as long; test wider in front than behind, becoming 



much flattened in adults; genital pores 2, 3 or 4 according to age .... josephinae. 

 Peristome about as long as wide; test not wider in front than behind; genital 



pores 3 (?) ovatus. 



Test distinctly narrower ; n front than behind ; genital pores 3 loveni. 



Test highest near middle; height more than half length; subanal fasciole longer than 



wide; periproct below posterior margin of test; genital pores 4 tkomsoni. 



