412 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



been pointed out, tlie single large dentate laterals of PecUnodonta may 

 represent, in the other division of the order, each a consolidation of the 

 three typical laterals of Acmcea. 



The name Onychoglossa has been used by G. O. Sars (1878) to denominate 

 the same group and as indicative of the same characters as those pos- 

 sessed by the Docoglossa (Troschel, 1801), as revised by me eight years 

 previously. I do not see any especial gain which might result to science 

 from substituting the newer for the older name. 



The relations of the groups may be expressed somewhat as follows : 



Order DOCOGLOSSA. 



Shell wholly external, dish-shaped, with apex anteriorly directed; 

 animal with two short tentacles, a non-extensible muzzle; branchijie 

 external or none ; renal and anal a[)ertures situated above the neck, 

 between body and mantle edge; no copulatory or external genital 

 organs ; mouth provided with a horny jaw aud long radula with pecu- 

 liar teeth ; dental formula not exceeding ., ,„„,>, ; metamorphosis of 



o {o'o) 6 



the embryo taking i^lace in the Qgg^ which is fertilized in the ovary. 



Suborder ABRANCHIATA. 



Animal without exlerjial branchiai. Embryonic shell spiral. 



Family LEPETIDtE. 



Subfamily Lepetince. Without eyes ; w ith a marginated muzzle ex- 

 tended into (on each side) a tentacular process. Uncini erect. Dental 



*■»'■'""'" 2l(R)n (' =2(3T3r2)- 



-p ^ ri ,. f Lepeta s. s. {-\- Filidium Forbes non Middendorf). 

 I Cryptohrancma Middendort. 

 Subfamily LepctelUnw. With eyes; other soft parts as in Lepeta. 



Uncinus scale like. Dental formula —--_-- ( ? = :, .^ ov i )• 



1 (z*J) 1 \ 1 (o+o) ly 



Lepetella Verrill. 



Suborder PROTEOBRANCHIATA 

 Animal with external branchiae. Embryonic shell conical. 



Family ACMiElDiE. 



I 



With a plumose cervical branchia ; with or without a branchial cordon j 

 muzzle frilled ; no rhachidian tooth. 



