126 FIELD MUSEUM OF NATURAL HISTORY 
family includes among other species the 'Tearl Oyster,” of 
which specimens are here shown. 
Case 11. — Pectinidce (Scallop Shells) ; SpondylidcB (Thorny 
Oysters) ; these two families contain many shells which are in- 
teresting on account of their forms and their brilliant colors. 
Case 12. — Ostreidce (Oysters) ; DentaliidcB (Tooth-shells) ; 
Chitonidce (Chitons) ; PatellidcB (Limpet Shells) ; Fissurellidce 
(Keyhole Limpets). 
Case 13. — Haliotidce (Ear Shells, Ablone). 
Case 14. — Turbinidce (Top Shells) ; Neritidce; NaticidcE; 
Xenop'horidcB. 
Case 15. — Capulidce (Cup and Saucer Limpets) ; Ampul- 
lariidcB (Apple Snails) ; Littorinidce (Periwinkles). 
Case 16. — MelanidcB; Turritellidce ; VermetidcB (Worm Shells, 
the shells being more or less contorted like worm tubes) ; 
CerithidcB. 
Case 17. — Strombidce (Conch Shells) ; CypraeidcB (Cowr- 
ies), a family containing some of the most beautiful shells 
known. 
Case 18. — Doliidce (Tun Shells) ; Cassidce (Helmet Shells). 
Case 19. — Tritonidc^ (Triton Shells). 
Case 20. — Muricidce, a large family of mostly spiny and 
roughened shells. 
Case 21. — NassidcB (Dog Whelks) ; Buccinidcs (Whelks) ; 
T urbinellidcB. 
Case 22.—rFasciolaridcr; Mitridce (Mitre Shells) ; Volutidce, 
a family containing many large and beautifully colored shells. 
Case 23. — MarginellidcE ; HarpidcB (Harp Shells) ; OlividcB 
(Olive Shells). 
Case 24. — Conidce (Cones), an extensive family living most- 
ly in warm seas. 
Case 25. — Terebridce (Auger Shells). 
Case 26. — Bullidce. 
Case 27. — Materials illustrating two groups of Mollusks, 
many of whose members have the shell rudimentary or wanting 
entirely. Many of these animals are represented here by beauti- 
fully executed glass models ; Limnaeidce. 
Case 2S.-—Limnaeidce continued; Stenogyridce, this family 
and the remaining ones, which belong to the order Pulmonata, 
are air-breathing Mollusks, the largest belonging to the genus 
