DESCRIPTION OF PLATES. 

 PLATE I. 



Galba reftexa (SAY). Animal removed from shell, dissected, and the organs 

 separated. 1, buccal >sac; 2, oesophagus; 3, gizzard; 4, crop; 5, intestine; 6, 

 pyloric portion of stomach; 7, rectum; 8, anus; 9, liver or digestive gland; 10, 

 salivary gland; 11, ducts of salivary -gland; 12, spire portion of body, containing 

 one lobe of the digestive gland; 13, penis-sac; 14, vas deferens; 15, anterior 

 protractor muscles of penis-sac; 16, posterior protractor muscles of penis-sac; 

 17, penis; 18, retractor muscle of penis; 19, retractor of penis-sac; 20, penial 

 opening; 21, vaginal opening; 22, duct of receptaculum seminis; 23, receptaculum 

 seminis; 24, first accessory albuminiparous gland; 25, second accessory albumin- 

 iparious gland; 26, oviduct; 27, uterine portion of oviduct; 28, albuminiparous 

 gland; 29, posterior portion of prostate; 30, anterior enlarged portion of pros- 

 tate; 31, prostatic portion of vas deferens; 32, ovisperm duct; 33, ovotestis; 

 34, ventricle; 35, auricle; 36, pericardiac cavity; 37, pulmonary vein; 38, plexus 

 of 'blood vessels on left lobe of kidney; 39, pulmonary sac or rete; 40, glandular 

 portion of kidney, or renal organ; 41, ureter; 42, cut edge of muscles connect- 

 ing head with velum; 43, velum; 44, muscular collar of velum; 45, cut edge of 

 head ; 46, tentacle ; 47, supra-esophageal ganglia ; 48, nerve to head or penis ; 

 49, nerve to penis-sac ; 50, nerve of female genital organs ; 51, columella muscles 

 and foot retractor muscles; 52, right retractor muscle of buccal sac. 



PLATE II. 



Figure A. Shell of Lymncea, to illustrate different parts. Much enlarged. 1, 

 spire; 2, aperture; 3, body whorl; 4, suture; 5, parietal wall; 

 6, columella or inner lip; 7, peristome or edge of outer lip; 

 8, umbilical chink; 9, sculpture of growth lines and spiral lines 

 producing the characteristic decussated appearance of the sur- 

 face. 



B. Young Lymncea just previous to its escape from the egg. 



C. Troohosphere stage of Lymnaa stagnalis LINNE. 1, mouth; 2, velum. 



(After Lankester.) 



D. Veliger stage of Lymncea stagnalis LINNE. 1, mouth; 2, velum; 3, 



foot; 4, tentacle; 5, eye; 6, shell (after Lankester). 



PLATE III. 



All figures are greatly magnified. 



Figure A. One-half complete row of teeth of Galba reftexa (SAY); c, central 

 tooth; 1-12, lateral teeth; 13-15, transition teeth; 16-33, marginal 

 teeth. X 300. 



B, Teeth of Lymncea stagnalis LINNE, to show position of central tooth 



in relation to lateral teeth. The first lateral to the left and the 

 first three laterals to the right are shown. Also, the two rows 

 and the median cusp of a third row. X 516. 



C. Lateral tooth of Lymncea showing named parts. 1, base of attach- 



ment; 2, reflection; 3, cutting portion of tooth; 4, entocorie or 



