46 AMERICAN JOURNAL 



Cyclostomv.s and of the other genera comprised in his Fam. 

 Cyclostomacea, but found no jaw existing. 



It is singular that Moquin-Tandom {Moll, de France, II., p, 

 891) in describing his Fam. Orhaces, in which are embraced 

 the species of Cychstomus, [sulcatus and elegans^) and of 

 Pomatias, occurring in France, gives as one of the characters 

 " Machoire nulle ;" he was correct, it would appear, as re- 

 gards Cychstomus, but in error as to Pomatias. 



The characters of the jaws are peculiar. It may be noticed 

 that Megalomastoma is placed by Pfeiffer in his Subfam. 

 Ptt.pinea^ with Registoma (P/iegostomcc, Troschel, which, as 

 shown above, is included by Troschel in Cyclotacea. An 

 examination of the jaw of Catcmhis and other genera em- 

 braced in Pupiriea may lead to interesting conclusions. 



The alliance of J/e5'o/o?72a.stoWK< and Cyclot'xs^ as regards the 

 form and arrangement of the teeth on the lingual membrane, 

 is shown by figure 2, plate 5, from examples of Megalomastoma 

 rylimlraceum, for which I am also indebted to Mr. Swift. 



The characters of the operculum in the Cyclostomacea are 

 doubtless of value in classification, but a complete examina- 

 tion of the animals will probably lead to modifications of the 

 methods adopted by Gray and Pfeiffer. The presence or 

 absence of the jaws would seem to be of equal, if not of more 

 characteristic value than differences in the operculum. 



I'roschel states that in the Fam. Selicinacea no jaw exists. 

 Whether it is found or not in the Fam. Proserpinacea, I am 

 unable to say. 



Note. — The figures are from drawings made by Mr. Edward S. Morse, 

 of Gorbam, Me., to wbom, for bis skill and care, in making the necessary 

 microscopic examination of the objects, I am under much obbgation. 



