94 A. M Verrill — Study of the family Pectinidce. 



Plate XVIII. 



Figure 1. — Chlamys irradians. Nuclear region of a young specimen showing the 



prodissoconch, or veliger shell, x 60. 

 Figure 2. — The same. Right side of a very young shell, x 1 5. 

 Figure 3. — The same. Right side of a somewhat larger specimen, showing two 



stages of growth, x 6. 

 Figure 4. — The same. Left side of a similar young specimen, x 6. 

 Figure 5. — Hyalopecten undatus. Left valve of the type-specimen, x H. By J. H. 



Emerton. (See Trans. Conn. Acad., vi, p. 444.) 

 Figure 6. — Camptonectes (Palliolum) vitrea. Right side of a mature specimen. By 



J. H. Emerton. 

 Figure 7. — The same. Hinge of right valve, x 6. 

 Figure 8. — The same. Hinge of lefl valve of the same specimen, x 6. 

 Figure 9, 9a. — The same. Sculpture of the left valve of a perfect specimen, x 21. 

 Figure 10. — The same. Right side of a very young specimen, x 16. 

 Figure 11. — The same. Left side of a somewhat larger example, x 12. 

 Figures 12, 12a. — Dorsal views of the right and left valves of the nuclear shell of a 



small specimen, x 60. 

 Figure 13. — The same. Side view of the nuclear shell, x 60. 

 Figure 14. — Camptonectes {Palliolum) striata. Inside of right valve, x 6. 

 Figure 14a. — The same. Sculpture of the left valve, x 24. 



Plate XIX. 



Figure 1. — Cyclopecten simplex Ver. (sp. nov.). Interior of left valve, x 15. 



Figure 2. — The same. Interior of right valve, x 15. 



Figure 3. — Cyclopecten pustulosus. Right side of a young specimen, showing the 



nuclear shell, x 12. 

 Figure 4. — The same. Left side of a slightly older specimen, x 12. 

 Figure 5. — Propeamusium thalassinum. Left side, x 12. 

 Figure 6. — The same. Interior of a right valve, x 9. 

 Figure 7. — The same. Hinge of left valve of the same example, x 9. 

 Figure 8. — Propeamusium ineqidsculpta. Interior of a left valve, x 8. 

 Figure 8a.— The same. Sculpture of the left valve, x 15. 

 Figure 9. — The same. Interior of a right valve of a young specimen showing the 



beginning of the internal ribs, x 9. 



Plate XX. 



Figure 1. — Chlamys irradians. Very young spat, much enlarged; p, nuclear or veli- 

 ger shell ; / foot ; g, rudimentary gill ; h, heart ; ad, adductor muscle ; a, anus ; 

 m, mantle ; e, ocelli ; t, tentacles. After Jackson. 



Figure 2. — The same. Left side of a very j'^oung living specimen, much enlarged ; /, 

 foot; a;, an opening through which water was ejected, showing an unusual pro- 

 trusion of the mantle border (perhaps accidental). 



Figures. — The same. Right side of a very young shell, much enlarged; n, byssal 

 notch and first pectinidial tooth ; p, p, prodissoconch or nuclear shell. 



