40 



AMERICAN JOURNAL 



toward Gadinia in their /rounded form, but are more closely 

 allied to the Siphonariidce. They cannot be affiliated to the Pa- 

 tellidce or Tecturidce. The following species were enumerated in 

 the paper alluded to, as having been definitely identified as be- 

 longing to this genus : A. borealis, Morton ; A. sexsulcatus, 

 alveolus, patelliformis, and subovatus, all of Meek and Hayden. 



The student who desires to pursue the subject further, will do 

 well to consult the Conchologia Iconica and the list of species of 

 Siplionarla given by Hanley in the Proc. of the Zool. Society of 

 London, 1858, page 151. 



References to Plate 4. 



Fig. 8. a, side view of Siph. thersites, with the shell removed, 

 b, view of same in the shell, from below. 



Fig. 9. Nervous system of Siphonaria Tristensis, Sby. 



Fig. 10. Dentition of Sip]w7iaria [Siphonaria) alternata, Say. 

 b, Rhachidian tooth. 

 a, section of 17th lateral. 



Fig. 11. Siphonaria [Liriola) peltoides, Dall ex Cpr. 



a, from above, enlarged one-fourth. 



b, side view. 



Explanation of Plate 5. 



Fig. 1. Dentition of Siphonaria [Liriola) tristensis, Sby. 



1" a, side view of 45th tooth. 



l"c, " " " l&t lateral 1" b, section of do. 



Fig. 2. Dentition oi Siphonaria [Liriola) thersites, Cpr. 



1' a, side view of 1st lateral. 



Fig. 3. Digestive and generative organs of Siphonaria tristensis, 

 Sby. From above. 



a, anus. j, jaw. 



b, genital bladder. 1, 1, 1, boundary of liver. 



c, crop. 1, a, left adductor muscle, 

 g, genital papilla. r, a, right " '• 

 m, buccal mass. p, a, posterior adductor. 



o, ovary, p, penis. 



r, rectum. s, salivary gland. 



st, stomach. t, testis. 



