NO. 2346. TWO NEW ACANTHOCEPHALOVS WORMS— VAN CLEAVE 463 



toto-mounts. In young individuals (fig. 10) the spines are easily ob- 

 servable, but in many of the fully mature specimens the body spines 

 can be demonstrated in toto-mounts only with greatest difficulty. In 

 fact, in some individuals they seem to be wanting and their place 

 marked only by a roughening of the body surface. This condition is 

 not peculiar to members of this genus, for the same thing has been 

 noted by the writer in describing mature females of FiUcollis lotulus 

 (Van Cleave, 1916: 132). 



The subcuticular nuclei of Quadrigyrus are unique, both in form 

 and in arrangement. Ovoid or elliptical giant nuclei of fixed num- 

 ber and arrangements are characteristic of the Neoechinorhyn- 

 chidae. P'inely dendritic nuclei are characteristic of Echinorhyn- 

 chus thecatus and what seem to be very minute scattered nuclei have 

 been frequently described in the subcuticula of various genera of 

 Acanthocephala. In Quadrigyrus nuclei of two distinctly different 

 types occur. In the anterior region of the body a single elliptical 

 giant nucleus is to be found in the subcuticula on the ventral surface 

 of the body, and directly opposite it on the dorsal surface of the 

 body there is another one just like it. The remainder of the sub- 

 cuticular layer contains a few large nuclei laterally arranged. Each 

 of these consists of an elongated central mass, from which a small 

 number of short heavy projections are given off. These branches 

 follow the canals of the lacunar system for a short distance and 

 end abruptly or in a short pointed projection. These nuclei last 

 described are different from any that have heretofore been recorded 

 from any acanthocephalan. 



From the foregoing discussion it will be seen that the genus 

 Quadrigyrus has certain definite points in common with the Neoe- 

 chinorhynchidae, on the one hand, and with the Rhadinorhynchinae, 

 on the other. These relationships are briefly recapitulated in the 

 following table : 



Even this partial summary of comparisons will show that it is im- 

 possible to include Quad7%gyrus in either of the two groups men- 

 tioned above; and since its affinities with other Acanthocephala are 

 much less obvious it becomes necessary to create for this genus a new 

 family, which takes the name Quadrigyridae and of which the genus 

 Quadrigyi'us becomes type. 



