1870.] 51 [Dall. 



Suborder Proteobranchiata Dall. 1870. 



Animal provided with three lateral teeth, with eyes and with ex- 

 ternal branchiae. Rhachidian tooth usually wanting. Uncini pres- 

 ent or absent. 



Family Acmjeid^: Carpenter. 



Shell patelliform ; animal provided with a free cervical branchia, 

 issuing from the left side of the body, above the head ; muzzle sur- 

 rounded with a frill of integument. Eadula without a rhachidian 

 tooth and with three lateral teeth on each side; with or without ac- 

 cessory uncini. 



A. Destitute of a branchial cordon. Acmcea. 



1. Acmsea Eschscholtz, 1828. Syn., Tecture Cuvier, 1830; Tec- 



tum Gray, 1847. 

 Teeth subequal, parallel in both axes; uncini absent; muzzle 

 frill produced into two lappets. 



Formula, 0(1 _ 1 _ 1 ? 1 _ 1 _ 1)0 - 



Type A. mitra Esch., Zool. Atlas, v, p. 18, no. 1. 1833. 

 Philippi. Zeit. f. mal., p. 106, 1846. 



2. Collisella 1 Dall, n. subg. 



(a). Third lateral smaller than, and opposed to, the second. 



First laterals anterior. Muzzle frill without lappets. A 



single minute uncinus on the pleura. 

 Formu la, 1(2 _-^_ 2)1 . 

 Type Acmcea pelta Esch., 1. c. no. 5. 1833. 

 (b) . Provided with two minute uncini on the pleura. (? Col- 

 lisellind). 



Formula, 2(2 . 1 ? 1 _2)2 - 



Type Patella saccharina Lin., Gmel., S. N., p. 3695, no. 19. 

 1792. 



B. Cordon present; interrupted in front. Lottia. 



1. Lottia (Gray) Cpr., 1863. Without muzzle lappets. Teeth as 

 in Collisella (a). 

 Formula, 



1 From Collis, a mound, in allusion to their shape. 



