On the Structure of the Mvuth in Suckiny Crustacea. 253 



present species is the sole known representative in tlie Euro- 

 pean seas, thus (at least analogically) connects the Brachio])oda 

 with the Conohitera throuj^h Ano/nia, the byssal plu«^ of which 

 has a sinular excavating or eroding power (sec * Ikitish Con- 

 chologv,' vol. ii. ]). .'52). Strong muriatic acid, subsequently 

 dilutecl, produced only a partial eflcct on the shells of /A athiu- 

 tica and /). striatii^ both of which contain a considerable jxjr- 

 tion of carbonate of lime, but are to a certain extent chitinous. 

 Crania is entirely calcareous. Professor King and ilr. 

 Davidson described D. atlantica as " corneous ;" Dr. Carpenter 

 says the shell of 1). lameUosa is "horny;" and M. Gratiolet 

 adds that Discina is composed of two layers, one " come " 

 and the other " calcaire." The outer or calcareous layer of 

 Discina is, according to Gratiolet, permeated by minute caical 

 canals, and the inner or " come " layer is imperforate ; but I 

 cannot help thinking that a further microscopic examination 

 would be desirable. Otherwise it is difficult to conceive how 

 there could be any connexion or communication between the 

 vascular system of the body or animal and the outer layer 

 of the shell, as exists in Terebratula and Crania. I cannot 

 find any perforated or tubular structure in D. striata. 



D. atlantica is probably the same species as the fossil from 

 the Coralline Crag at Sutton, which Mr. S. Wood at first 

 doubtfully named D. norvcjica, and afterwards D. fallens ; 

 and which Mr. Davidson at first doubtfully named Orhicula 

 lameUosa, and since D. fallens (see Ann. and ^lag. Nat. Hist. 

 1840, and the Pala;ontographical Society's Publications for 

 1852 and 1874). But Orhicula norvegica of Sowerby {=0. 

 larnellosa, Broderip) is a very different and tropical species of 

 Discina (see also Trans. Linn. Soc. vol. xiii. p. 465, and the 

 ' Malacological and Conchological Magazine,' 1838, ]jp. 19-23). 



XXIII. — On the Structure of the Mouth in Sucking Crustacea. 

 By Professor J. C. SCHIODTE*. 



[Continued from * Annals," 1868, 4th ser. vol. i. p. 25.] 



II. Anthuka. III. Laphystius. 



16. Next to Cyinothoidai, though as a type of a separate 

 family, the genus Anthura must be placed. 



Tiie specimens which have served for the following exami- 

 nation belong to Anthura carinata, Kriiyer (Naturh. Tidsskr. 



• Transilated and partly condensed, with the sanction of the author, 

 from 'Naturhistorixk Tids5krirt,'."^rd ser. vol. x. Copenhapen, 1875, w-ith 

 five plates (explanations in Latin). The first part (Cyniothose) was 

 translated in the • Annals," 1808, -llli series, vol. i. pp. 1-20. 



