On the Structure of the Mouth in Sucking Crustacea. 253 



present species is the sole known representative in the Euro- 

 pean seas, thus (at least analogically) connects the Brachiopoda 

 with the Conchifera through Anomia, the byssal plug of which 

 has a similar excavating or eroding power (see ' British Con- 

 chology,' vol. ii. p. 32). Strong muriatic acid, subsequently 

 diluted, produced only a partial effect on the shells of Z^. atlau- 

 tica and D. striata, both of which contain a considerable por- 

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

 Crania is entirely calcareous. Professor King and Mr. 

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

 says the shell of D. lamellosa is "horny;" and M. Gratiolet 

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

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

 Discina is, according to Gratiolet, permeated by minute cgecal 

 canals, and the inner or " cornd " 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 shellj as exists in Terehratula and Crania. I cannot 

 find any perforated or tubular structure in 1). 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, norvegica, and afterwards D. fallens ; 

 and which Mr. Davidson at first doubtfully named Orhicula 

 lamellosa, and since D. fallens (see Ann. and Mag. Nat. Hist. 

 1840, and the Palseontographical Society's Publications for 

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

 lamellosa, 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, pp. 19-23). 



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

 By Professor J, C. Sghiodte*. 



[Continued from ' Annals,' 1868, 4th ser. vol. i. p. 26.] 



II. Anthura. III. Laphystius. 



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

 family, the genus Anthura must be placed. 



The specimens which have served for the following exami- 

 nation belong to Anthura carinata, !K!royer (Naturh. Tidsskr. 



* Translated and partly condensed, with the sanction of the autlior, 

 from ' Naturhistorisk Tidsskrift," 3rd ser. vol. x. Copenhag-en, 1875, with 

 five plates (explanations in Latin). The first part (Cyraotho;©) was 

 translated in the ' Annals," 1868, 4th series, vol. i. pp. 1-25, 



