504 Mr. H. A. Bay lis on 



fifty stout bundles dorsal ly and a similar number ventrally. 

 There is no very clear distinction into outer and inner layers. 

 Tlie genital ducts pass l)€tween tlie dorsal and ventral excre- 

 tory vessels and ventraily to the longitudinal nerves. 



Tins form differs from T. erostru (Lonnberg), which occurs 

 in the same host, in the larger size of the scolex, the slight 

 development of the auricular appendages, the larger number 

 of testes, and other details. 



liesocestoididsB. 

 Mesocestuides Vuieratus (Batsch). 



Host : Vulpes vulpes (red fox). Yukanski, 23. vii. 1917. 

 This species occurred in considerable numbers in the upper 

 part of the small intestine. 



Davaineidse. 

 Davatnea tetragona (Molin), var. lagopodis (var. n.). 



Host: Laqnpus mutus (ptarmigan). Murmansk, Kola 

 Inlet, 2. vi. 1917. 



Two specimens of a Davairwa closely resembling D. tetra- 

 gona (Molin) were found in a ptarmigan killed at Kola Inlet. 

 This species is stated by Clerc^ to occur in Lagopus alhus'\ 

 in the Ural, but the present examples show certain pecu- 

 liarities that seem to indicate a distinct variety. 



The length of a complete specimen is about 20 cm. and 

 the maximum width 5 mm. Tlie scolex measures 0*3 mm. 

 across. The suckers are oval,^ their longest diameter (antero- 

 posteiior) being about O'li mm. The diameter of the 

 rostelluni is 0"055 mm. It is armed Avith a single row of 

 minute hooks, 8 /x long. The suckers are armed with several 

 rows of very small booklets. 



There is a considerable unsegmented neck, as in the typical 

 D. tetragona. The segments are much broader than long, 

 except tlie gravid ones near the posterior end. The trans- 

 verse excretory vessels are very wide, often appearing as 

 wide as the medullary portion of the segments between them. 

 The genital pores are unilateral ; the cirrus-sac is small 

 (0*15 mm. long), but muscular. The vas deferens is con- 

 siderably coiled, but, as a w liole, pursues a fairly straight 



* Bull. Soc. Oural. Sci. uat. xxx. 1910, p. 123. 



t The bird refeiTed to as Z. alius seems more likely to have been 

 L. mutus. The former, as 1 am informed by ^Ir. C. Chubb, is an 

 American form, though it ranges into Scandinavia and Northern Eussia. 



