186 Prof. T. Rupert Jones on 



ventral slit (like the opening of the hood in some Phyllopods) , 

 crossed by a bridge of shell-matter. Dr. Riehter's views of 

 the relationship of the so-called " Cypridinen," described and 

 figured in the ' Zeitschrift ' for 1869 are there given with 

 some doubt ; and we now know (see above, p. 183) that he 

 refers them to Entomis. 



EXPLANATION OF PLATE XI. 



Fiy. 1. Concave cast, with faint knob and ridge (the latter extended 

 by pressure). Furrow-casts interrupted by slight indentations 

 due to the serrulation of the riblets. Riehter's pi. xx. fig. 10 

 (Zeitschr. 1869) makes the nearest approach to the typical in- 

 terruption of the furrow-casts. This specimen (referred by Dr. 

 Richter to " C. serratostriata "), is in a red schist, with many 

 casts, hollow and raised, elongate, oval, and rouud. 



Fig. 2. Concave cast, squeezed so as to give the furrow-casts a lozenge- 

 shape arrangement. On similar schist to that of fig. 1, and 

 referred to the same species. It may be the same as fig. 6 

 (" tenella *'), or possibly fig. 9 (" labyrinthica "). 



Fiy. 3. Convex smooth cast (marked with sand-granules only) of a valve 

 squeezed up endways on itself, with the nuchal depression 

 exaggerated by the pressure, and a mark below of the test 

 broken across. With fig. 1, and referred to the same species. 



Fig. 4. Shallow concave cast, with faint irregular knob and ridge. The 

 furrow-casts are much interrupted by what seem to be the 

 bases of external spines, along the internal lines. On reddish- 

 grey schist. This is referred by Dr. Richter to " C. gyrata." 



Fig. 5. Small hollow cast, with ridge and slight knob. On red schist, 

 with numerous casts, both raised and sunken, long, oval, and 

 round. On this hand-specimen occur such smooth convex 

 casts, with central pit, as that shown in Riehter's ' Beitrag,' pi. ii. 

 fig. 27. Referred to " C. scrobiculata, Richter," but probably 

 E. serratostriata. 



Fiy. 0. Hollow casts of a pair of opened valves, with ridges within, which 

 represent the nuchal furrow of each valve. In dull purplish- 

 red schist. Referred to "C. tenella, Richter," but corresponding 

 in some respects with "C. labyrinthica" Richter (see fig. 9). 

 The smoothness of the delicate costulse and their circular 

 arrangement may be distinctive features ; but, on the other 

 hand, these may possibly be modifications from pressure. The 

 figured " tenella' 1 '' ('Zeitschr.' 1809, pi. xx. fig. 11) has concen- 

 tric riblets ; but they are pitted. 



Fig. 7. Hollow cast (somewhat crushed) with ridge and knob. In dark- 

 grey schist, with both concave and convex casts, variously 

 squeezed. Referred to " C. tceniata, Richter," but probably E. 

 serratostriata. 



Fig. 8. Convex, somewhat flattened, cast ; in purplish-grey schist, with 

 both raised and hollow casts, but low and shallow. Riblets 

 strong and slightly serrulate. Referred to "C. gyrata, Richter." 



Fig. 9. Shallow hollow cast, with the furrow-casts much modified by 

 pressure. In pale purplish-grey schist, with a few shallow and 

 imperfect casts. Referred to " C. labyrinthica, Richter," with 

 the figure of which (in 'Zeitschr.' 1869, pi. xx. fig. 12) it 



