ART. 7 



A NEW EHIZOCEPHALAlSr PARASITE BOSCHMA 



somewhat less regular by being partially worn off, but on the whole 

 they have the same form and size. 



The two layers of the external cuticle have approximately the 

 same thickness, which in the lateral parts of the mantle is about 

 275m- With a number of folds and irregular excrescences the two 

 cuticular layers project into the mantle, causing thereby the wrinkled 

 appearance of the whole animal. 



The mantle is highly muscular; in transverse sections a number of 

 muscular elements are visible, which constitute the transverse mus- 

 culature of the mantle. Moreover, many of the epithelial muscular 

 cells connect the external and the internal cuticle. Besides the 



'^^^^-^^ 



4mwm. 



Figure 7.— Briarosaccus callosus. a, Section through the mantle, showing the two 



LAYERS OF THE EXTERNAL CUTICLE, THE INTERNAL CUTICLE, AND THE EPITHELIUM, MUSCLES, 

 AND LACUNAE OF THE MANTLE. X 18. 6, EXCRESCENCES OF THE EXTERNAL CUTICLE, SEEN FROM 

 ABOVE. X 660 



muscles and the epithelium the mantle contains several lacunae of 

 different sizes. 



As the external cuticle the internal chitinous sheath of the mantle is 

 strongly developed; it may even attain a thickness of 50^. Its surface 

 is rather irregular and wrinkled, and bears a large quantity of well-de- 

 veloped retinacula, two of which may be seen in the section represented 

 in Figure 7a. The retinacula of Briarosaccus (fig. 8) differ from those 

 of Peltogaster by their great number of spindles. They occur in 

 abundance on the lower surface of the internal cuticle (fig. 8a) and vary 

 in size from 75^ to over 200^. A few more strongly enlarged retinac- 

 ula are represented in Figures 8l-d, from which may be seen the 

 strong variability in the shape of these organs and of their spindles. 

 Not only the number of spindles in each retinaculum is different (this 



