40 THOS. H. MONTGOMERY, 



but the species agricola and rodericana are so little known, that 

 Bürger is unwarranted in referring them to Geonemertes. Also the 

 union of AmpMporus and Drepanoporus in the family Amphiporidae 

 is unsatisfactory; for the latter genus should rather be granted family 

 rank, after Verrill's precept ('93), on the ground of its rhyncho- 

 coelomic diverticula, and large number of central stilets, in which 

 points it is sharply distinguishable from all other Metanemerteans. 



As a satisfactory classification of the closely interrelated Meta- 

 nemertean genera, is very difficult to formulate ; still more difficult is 

 the establishment of their genetical relationships, based upon a study 

 of their structural similarities. And I would suggest here, prelimi- 

 narily, that the supposed genetical relationships exhibited in the 

 "family tree" of this group, which Bürger presents, by no means 

 stand in complete accord with his own careful histological and ana- 

 tomical investigations. And this "Stammbaum" would indicate that 

 Bürger himself has doubts as to the homogeneity of his family 

 ProsorJiocJimidae, since he derives Prosorliochmus and Prosadenoporus 

 from Eunemertes, but Geonemertes from Amphiporus . 



The species Tetrastemma catenulatum was described by Verrill 

 ('93), and classed by him as a var. catenulatum of T. vermiculum. I 

 have separated it as a distinct species, T. catenulatum (Verr.), from 

 T. vermiculum (Stimps.), on the ground of its metameric pigment 

 mottlings, which extend posteriorly to the anal region, and are never 

 absent, while in the typical vermiculum only two longitudinal pigment 

 stripes occur, namely between the anterior and posterior pairs of 

 eyes. I have described above histological differences of the two, in 

 regard to the distribution of this pigment. T. vermiculum I found 

 exclusively at Newport, R. I., and T. catenulatum exclusively at 

 Wood's Holl, Mass. 



Wistar Institute of Anatomy and Biology, 

 Philadelphia, April 17, 1896. 



