with Descriptions of the new Species. 



375 



Alulae. Lateral teeth none in the adult. Young with a distinct hinder 

 lateral tooth. 



Inhabits coast of Europe ; and Fossil near Rome. 



7. Lutrdria zealdndica Gray. Shell compressed, 'smooth, high, rather 

 truncated at each end beneath. Hinder lateral teeth wanting in the 

 adults. 



Inhabits New Zealand. 



** Shell oblong, very gaping and reflexed behind, and marked with an oblique 

 posterior Ridge. Lateral Teeth distinct. 



8. Lutrdria recurva ; Mactra recurva Gray, Wood Sup., t. 1. f. 2. ; Mactra 

 papyracea Lam. (not Syn.), Sow. Gen., f. 1. 



9. Lutraria Cyprinus ; Mactra Cyprinus Gray, Wood Sup., t. I. f. 1. 



*** Shell thin, gaping behind, with a Ridge. Hinder lateral Teeth distinct. 



10. Lutrdria campechensis ; Mactra eampechensis Gray, List., t. 308. f. 141. ; 



V. Muli'nia. 



33 



Wood Sup., t. 1. f. 3. 



Shell ovate, trigonal, subangular at each end. Cardinal and lateral teeth 

 like Mactra. Siphonal inflection ovate, distinct. Ligament internal ! in a 

 triangular groove in the upper surface of the deep oblique cartilage' it, 

 quite hid from view. 



This genus, and Gnathodon, are the only bivalves that I am acquainted 

 with which have the ligament internal. In all the other shells, even those 

 which have internal cartilages, the ligament is external, and placed on the 

 outer part of the cardinal edge of the shell. The hinge margins of the 

 adult shell of this genus are sometimes much enlarged, the umbones being 

 separated at a considerable distance from one another by a distinct area, 

 as in the genus A'rca. This area, instead of showing the groove of the 

 ligament, as in that genus, is only marked with a slight oblique line, indicat- 

 ing its position ; and this line is often so obscure as scarcely to be dis- 

 tinguished. This shell may be regarded as a specimen of the last form 

 in which the upper surface of the ligament has been covered with a shelly 

 plate. 



a. Hinder Slope circumscribed with a raised Line. 



1. Mulinia typicus n. s. Shell ovate, suborbicular, convex, solid. Um- 

 bones wide apart. Area lozenge-shaped. Lateral teech very short, high, 

 thick, round. The cartilage pit prominent into the cavity of the shell. 



Inhabits . 



2. Mulinia bicolor n. s. Shell ovate, rather convex, solid, white. Um- 

 bones and hinder slope orange, varied. Lateral teeth short, compressed, 

 triangular. Cartilage pit prominent into the cavity of the shell. Young 



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