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H. J. Van Cleave 

The genus Neorhynchus was founded in 1892 by Hamann to include 
Echinorhynchus rutili Muller and Echinorhynchus agilis Rudolphi. 
Practically all investigators dealing with the Acanthocephala since that 
date have accepted this generic name. Recently attention has been 
called to the fact that the name Neorhynchus is preoccupied. Sclater, 
in 1869, and, again, Milne Edwards, in 1879, employed it for other 
groups. In accordance with the laws of nomenclature, it then becomes 
necessary to reject the name Neorhynchus as applied to Hamann's 
genus. I propose the name Eorhynchus to designate these forms. 
While all other investigators dealing with this genus have been limited 
to a study of the two original species, it has been my good fortune to 
include five additional species in a comparative study, the results of 
which have led me to a restatement of its essential characteristics. 
As pointed out in an earlier paper (1913), I consider the following 
points as diagnostic for this genus of Acanthocephala: 

1. Six giant nuclei in the subcuticula arranged, normally, five in 
the middorsal line of the body and one in the midventral line. 

2. Two giant nuclei in one lemniscus and only one in the other. 

3. Proboscis receptacle with but a single muscle layer in its wall. 
In the light of this analysis, the contentions of de Marval (1904: 

582) and of Monticelli (1905:217), that Apororhynchus hemignathi 
Shipley should be included in this genus are based on an inadequate 
understanding of its natural limits. 

Shipley, in his description of A. hemignathi (1896:210), wrote: 
"As in Neorhynchus, the number of nuclei is very small, some twelve 
to twenty seem to suffice for the whole subcuticle, and perhaps two to 
four for each lemniscus. The nuclei are scattered about in a most 
irregular fashion. . . ." 

I have shown (1913) that not alone the presence of giant nuclei, but 
more strikingly their number and arrangement furnish a sure criterion 
for the determination of members of this genus. Shipley's genus 
Apororhynchus, because of its radical departure from the typical struc- 
ture of the Eorhynchi, cannot be included within the genus Eorhyn- 
chus. The valid species of this genus are, then, Eo. rutili (Muller 

* Contributions from the Zoological Laboratory of the University of Illinois, 
under the direction of Henry B. Ward, No. 32. 


1784), Eo. agilis (Rudolphi 1819), Eo. emydis (Leidy 1852), Eo. 
gracilisentis (Van Cleave 1913), Eo. longirostris (Van Cleave 1913), 
Eo. cylindratus (Van Cleave 1913) and Eo. tenellus (Van Cleave 

Hamann (1892) also created the family Neorhynchidae for the 
single genus Neorhynchus. Porta ( 1907 : 409) accepted Hamann's 
revision of the Acanthocephala only in part, recognizing but two 
families, Echinorhynchidae and Gigantorhynchidae, and included Neo- 
rhynchus under the former. The characteristics already listed as diag- 
nostic for the genus Eorhynchus, together with the complete fusion of 
the cement glands, are such essential features that the inclusion of 
Eorhynchus in the same family with Echinorhynchus would so distort 
our conception of the family Echinorhynchidae that it would cease to 
be a natural division of the Acanthocephala, and would become a 
purely artificial assemblage. In view of these facts I consider that the 
evidence fully justifies the retention of the family rank originally 
attributed to these forms for which the family name now becomes 

The writer's extensive studies on the cytology of the Eorhynchidae 
furnish conclusive evidence in support of the foregoing arguments. 
These studies in detail appear in the June number of the Journal of 


Hamann, O. 1892. Das System der Acanthocephalen. Zool. Anz., 15: 195. 

de Marval, L. 1904. Sur les acanthocephales d'oiseaux. Note preliminaire, 
Rev. suisse de zool., 12 : 573-583. 

Monticelli, F. S. 1905. Per una rettifica. A proposito di una proposta 
classificazione degli Acantocefali. Boll. Soc. Natural. Napoli, 19: 217-218. 

Porta, A. 1907. Contributo alio studio degli Acantocefali dei Pesci. Bio- 
logica Torino, 1:377-423. 

Shipley, A. E. 1896. On Arhynchus hemignathi, a new genus of Acantho- 
cephala. Quart. Jour. Micr. Sci., 39: 207-218. 

Van Cleave, H. J. 1913. The Genus Neorhynchus in North America. Zool. 
Anz., 43: 177-190.