244, Dr. G. C. Wallich on the Difflugian Rhizopods. 
front and side views of the extreme variety, D. cassis*, in which 
it will be seen that the characters of the marsupiform series attain 
their maximum development. The well-marked inversion of the 
lip and the extreme excentricity at once denote this form as being 
the furthest removed from that in which the lip is everted, namely 
D. lageniformis (2c). 
Lastly, fig. 1 y represents D. Arcella as a subspecies springing 
directly from the embryonic form. - In it we perceive the reappear- 
ance of the inverted lip, whereby it is allied to the marsupiform 
series, and the vertical depression which, in some of the plain 
globular forms, renders it so difficult to determine whether the 
specimen presenting it 1s an aberrant D. Arcella or D. globularis ; 
whilst at fig. 1 z is given a member of the allied Actinophryan 
subfamily, the Euglyphide, related to Difflugia Arcella both in 
virtue of its purely chitinoid test and the nature of the surface- 
marking in one of the species (EL. margaritacea). Difflugia Arcella 
hence constitutes the connecting-link between the two subfamilies. 
PLATE XVI. 
‘ig. 1. Side view of a young specimen of the subspecies D. globularis ; 
1 a, front view, showing aperture. 
Fig.2. Side view of somewhat advanced state of the same; 2a, front 
view. 
Fig. 3. Side view of the early stage of the oblique or marsupiform series ; 
3a, front view. 
Figs. 4 & 4a. Same views of a still more advanced stage of the same. 
Fig. 5. Side view of horned variety of D. marsupiformis ; 5 a, front view. 
Fig. 6. D. cassis, side view; 6a, front view. 
Fig. 7. D. mitriformis, showing presence of the usual sandy granules on 
the posterior four-fifths of the test, whereas the anterior fifth is 
composed of chitinoid cylinders. (This form was figured by me, 
but very imperfectly, in the ‘Annals’ for June 1863, PI. 10. fig. 12.) 
Fig. 8. Two-horned specimen of D. mitriformis. 
Fig. 9. D. pyriformis, from Greenland, showing how completely the test 
is made up of frustules and valves of diatoms (Munotia and Ta- 
bellaria). 
Fig. 10. Common form of D. pyriformis, showing moderately large sandy 
granules. 
Fig.11. D. acuminata, made up of tabular mineral particles. 
Figs. 12, 12 a, 126, 13a. Small specimens of mitriform and acuminate se- 
ries. In fig. 12 a crystalline body has been added to the test. 
Figs. 13 & 14. Oblong variety, showing the apertural band. 
Fig.15. D. lageniformis, showmg incipient eversion of lip. 
Fig. 16. D. lageniformis, mature specimen, showing hyaline everted margin 
of the lip. 
Fig. 17. D. eta, typical form, but made up of large sandy particles. 
Fig. 18. D. tuberculata, mineral matter consisting, m a great measure, of 
minute diatoms. The test of this form is mulberry-shaped. 
Fig.19. D. corona, front view, showing crenulate margin of aperture; a 
six-horned variety. 
Fig. 20. A somewhat smaller four-horned variety; side view. 
Fig. 21. D. globularis, from Greenland, chiefly made up of minute diatoms. 
Fig. 22. Plain variety of D. aculeata, showing the transition from the 
plain globular to the oblique form, and the incipient version of 
the margin of the aperture. 
* Cassis, a helmet. 
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