JOUSSEAUMIA. 



EXPLANATION OF PLATES. 

 LETTERING IN ALL THE FIGURES. 



A. ad., anterior adductor muscle. 



A. op., anal or exhalant aperture. 



An., anus. 



A.r.p., anterior retractor pedif? muscle. 



Br.m., branchial muscles. 



Bucc., buccal cavity. 



By., byssus. 



By.c., byssus cavity. 



By.g., byssus groove. 



By.gl., byssus gland cells. 



Ccec., caecum. 



C.g., cerebro-pleural ganglion. 



Cr.s., crystalline style. 



Cu., cuticular lining of stomach. 



Dbr., internal demibranch. 



P., foot. 



fr., frontal cilia. 



gl.c., glandular cells of stomach. 



Go., gonad. 



Go.a., genital aperture. 



Go.c., gonaduct. 



Go.d. 1 , dorsal diverticulum of gonad. 



Go.d. 2 , ventral diverticulum of gonad. 



Hi., ventricle of heart. 



if.j., interfilamentar junctions. 



il.j., interlamellar junctions. 



L, lateral cilia. 



I.e., oblong cells bearing lateral cilia. 



If., latero-frontal cilia. 



Li., liver. 



Liy., hinge ligament. 



Lm.int., internal lamella of demibranch. 



Lm.ext., external lamella of demibranch. 



L.p., labial palps. 



M., mantle. 



Oe., oesophagus. 



w.exh., exhalant or anal pallial orifice. 



of., otocyst. 



P.ad., posterior adductor muscle. 



PC., pericardium. 



P.g., pedal ganglion. 



P.r.p., posterior retractor pedis muscle. 



P.s., pallial suture. 



Ptr., protractor pedis muscle. 



Ptr. 1 , ventral slip of the protractor pedis 



muscle. 

 Pi., rectum. 

 Re., kidney. 

 Re.a., renal aperture. 

 Re.d., renal duct. 

 R.pd., reno-pericardial canal. 

 St., stomach. 

 Spz., spermatozoa. 

 Fb., vestibule of gonad. 

 Vc., visceral commissure. 

 Fg., visceral ganglion. 

 Vs., vesicula seminalis. 

 x., cells of the interfilamentar junctions. 



PLATE I. 



Fig. 1. An adult specimen of Jousseaumia heteropsammice lying in the right valve of the shell, x 85. 

 2. Valves with hinge teeth of /. heterocyathi. x 85. c., the single cardinal tooth of the right valve ; 



c.a., the anterior, and c.p., the posterior cardinal teeth of the left valve; foss., ligamentar fossa; 



lig., ligament; l.ant., anterior lateral, and l.post., posterior lateral teeth; L.F., left valve; 



R.F., right valve. 



3. Valves with hinge teeth of /. heteropsaminuu. x 85. Lettering as in the preceding figure. 

 4. Section through the byssus groove of J. heteroci/athi highly magnified, showing the ciliated 



demicanal, d.c., in the depth of the groove ; mus., muscle fibres of the foot. 

 5. A section through the duct of the byssus cavity, higher up than fig. 4. The ciliated demicanal, 



d.c., retains the same shape as in fig. 4 ; the remainder of the duct is not ciliated, but lined by 



a thick cuticle formed by the underlying epithelial cells. 



2 M 



