272 PALAEONTOLOGY OF NEW YORK. 



Genus MIMULUS, Barrande. 1879. 



PLATE Xlc, PIGS. 23-32. 



1878. Splrifera (.»), Miller and Dykr. Journal Cim-innati Soc. Nat. Hist., vol. i, p. 37, jil. ii, fig. 3. 



1879. Triplesia, Hall. Trans. Albany Institute, vol. x. Abstract, p. 16. 



1879. Mimulus, Barrande. Systtnie Silurien An Centre fie la Bohfime, vol. v, p. 10'.), pi. ], dg. iii ; 



pi. 9, tigfs. iii, iv, vi. 

 1882. Triplesia, Hall. Eleventh Ann. Rejit. State Geologist of Iniliana, p. 298, pi. xx\ii, tig.i. 19-22. 

 1889. Streptis, Bbbchbk ami Clarki5. Memoirs N.Y. State Museum, vol. i. No. i, p. 30, pi. iii, figs. 9, 10. 



The affinities of this peculiar group of fossils have not hitherto been cor- 

 rectly understood. M. Barrande has given no clue to the interior characters 

 of the shells, and as the genus has been recognized only in the Bohemian basin 

 it has not been closely studied by other authors.* After a careful comparison 

 of M. Barrande's figures of the Bohemian species with the fossil known as 

 Triplesia pu'illus, Hall, or Spirifera Waldronmsis, Miller and Dyer, from the Niagara 

 fauna of Indiana, there remains little doubt of their being congeneric forms. 



The DIAGNOSIS of the genus, given by M. Barrande, is in the following 

 terms : 



" Cette forme extrrieure est completement inverse de celle de Spirifer, en ce 

 que le bourrelet, jjien marque, se trouve sur la valve ventrale, tandisque le sinus 

 correspondant se montre sur la valve dor sale. 



" La charnii-re est droite, mais n'occupe pas toute la largeur du fossile. L'aiva 

 l)ien di'veloppre pn'-sente sous le crochet une ouverture triangulaire, fermt'-e par 

 uii deltidiuni, jusqu'au crochet. Celui-ci parait conserver un petit trou roiid, 

 que nous observons sur un spt'-cimen non figurr. 



" II est rare de pouvoir observer le deltidiuni, parceque la trace de la soudre 

 avec I'area est comph-tement efface''. 



" Les 2 especes typicpies, Mim. perversus et Mim. moera, PI. 9, prt'sentent ex.ac- 

 tement les caractt-res, que nous venous d'exposer." 



The exterior form of these shells is subtriliedral like Triplegia, and is 

 subject to some variation, for of the three species described by M. Barrande, 

 two, M. perversus and M. moera, have the strong median fold on the pedicle- 



* ZiTTBL (Han<lbnch der Palseontologie, vol. i, p. 684) made it a sub-genus of Spirifer, and CErlkrt 

 (Fischer's Manuel de Conehyliologie ; Brachiopode.s, p. 1313) placed it with doubt under the family Bhyn- 



CHONF.I.LW.E. 



