AKERA. 377 



The shell of this genus is peculiar in its sutural sinus or slit, and 

 the wholly exposed s])ire. The animal is characterized by the very 

 long and narrow head shield, the epipodial lobes being as in Hami- 

 nea. The dentition also resembles that of Haminea, but the stom- 

 ach is differently armed. 



The young animals use the epipodial lobes as swimming organs, 

 flitting about like butterflies. 



A. BULLATA Miiller. PI. 42, figs. 11, 12, 17. 



Shell fragile, ovate, squarely truncated above, the spire nearly 

 flat and encircled by an acute keel as in A. soluta ; covered with a 

 thin pale brownish epidermis ; surface densely microscopically 

 striated. Aperture nearly as long as the shell, narrow above and 

 deeply sinused, gradually widening below, becoming broadly round- 

 ed at base ; outer lip arched forward in the middle ; columella sim- 

 ply arcuate with a thin reflexed, appressed callus. Alt. 14, diam. 

 d mill., sometimes larger, alt. 28 mill. 



Norway and seas of North and West Europe generally ; Mediter- 

 ranean. 



Akera hnllata Mull., Zool. Danica, p. 242, pi. 71, f. 1-5 (1776). 

 —Forbes & Hanley, Hist. Brit. Moll., p. 527, pi. 114d, f. 4-6 

 (shell) ; pi. vv, f. 6 (animal). — SowB., Conch. Icon., f. 6. — Acera 

 bullata Meyer & Mobius, Fauna Kieler Bucht., p. 81, plate (ani- 

 mal).— Sars, Moll. Reg. Arct. Norv., p. 281, pi. 26, f. 1 (shell), pi. 

 xii, f. 17 (dentition, anatomy). — Langerhaus, Zeitschr. Wissensch. 

 Zool., xxiii, p. 171, pi. 8 (embryology), abstract in Zool. Rec, ix, p. 

 151. — Mazzarelli, Zool. Anzeiger, xiv, p. 241, f. 6 (genitalia). — 

 Vayssiere, Rech. Moll. Opisth., p. 23. — Jeffreys, Brit. Conch., 

 iv, p. 430; V, pi. 95, f. l.—Aceras bullatum Locard, Coq. Mar. France, 

 p. 24, f. n.^Bulla akera Gmel., Syst. Nat. (13), p. 3434, and of 

 Montagu, Fleming, Dillwyn, Wood, and other early English 

 conchologists. — B. norvegica Brug, Encycl. Meth., i, p. 377, pi. 

 360, f. 4. — Bulla resiliens Donovan, Nat. Hist. Brit, shells, pi. 79, 

 (1804).— 5. fragilis Lam., An. s. Vert. (edit. Dh.) vii, 672.— 

 Blainv., Man. Malac, pi. 45, f. 7.— Sows., Conch. Man., f. 247.— 

 Akera flexilis Brown, Hlustr. Conch. G. B., p. 59, pi. 19, f. 31, 32. 

 —B. {A.) bullata A. Ad., Thes. p. 572, pi. 121, f. 41.—^. (A.) 

 hanleyi A. Ad., I. c. p. 573, pi. 121, f. 46. — Eucampe donovani 

 Leach, Syn. Moll. G. B., p. 42. — Bulla canaliculata Olivi, et. at., 

 and possibly of Linnaeus, see Hanley, Shells of Linn., p. 207. — 



