4 BRITISH MARINE TESTACEOUS MOLLUSCA : 
SYNOPSIS OF THE FAMILIES AND GENERA OF THE BRITISH TES- 
TACEOUS ACEPHALA, GASTEROPODA, AND CEPHALOPODA, 
DISTRIBUTED IN SIX DIVISIONS, ON THE BASES OF SEXUAL 
ORGANIZATION. 
First Division. 
ACEPHALA PALLIOBRANCHIATA. 
Hermaphrodita, sine concubitu. 
TEREBRATULIDE .. 1.2... » +. «> sg ELypObhyris. 
Terebratula. 
Argiope. 
CRANPAD AGO. a? Ee EY A Crane 
Second Division. 
ACEPHALA LAMELLIBRANCHIATA. 
Hermaphrodita, sine concubitu. 
* Mantle open, no tubes. 
ACN GINUWAIDIADS Ser cyanea ae AI OTIS 
IRECRINIDE Sek oo. ae eee tee oleecten: 
OsTreapm es 3 eee SS Ostrea: 
** Mantle open, no siphonal tubes or sessile. 
Miyriuiat. 5 2):: os.05 Gee i te cis ESS 
Dreissena. 
Modiola. 
Crenella. 
Pinna. 
Avicula. 
TCO UDA a cs = 66 os Siena ceo one MIO: 
Anodon. 
*** Mantle open, tubes sessile or short. 
PARA ere oy ce ha ne ote eae herote ie SEN: 
Pectunculus. 
Nucula. 
Leda. 
Galeomma. 
¥ Lepton. 
