BRACmOPODA. 25 



development of its platforms and other interior characters, close upon Lingulops, 

 the genus which presents the first deviation, in this direction, from Lingula. 

 Externally, neither Lingulops nor LingulaSiMa may be distinguished from Lln- 

 GULA, but, notwithstanding this exterior linguloid aspect, both exhibit the most 

 positive affiliations with the genus Trimerella. Lingulasma is represented by 

 a single species, and by the favor of Mr. Charles Schuchert wc have had at 

 our disposal a numljer of specimens from the Hudson group at Wilmington and 

 Savannah, Illinois, including the internal cast which has served Mr. Ulrich the 

 purposes of generic diagnosis. These specimens preserve both external and in- 

 ternal features, the cast referred to being in a most favorable condition for study. 

 In strong contrast to the minuteness of Lingulops is the very considerable 

 size of Lingulasma, and though this difference fails to affect the external linguloid 

 character of the shell, it is to be regarded, in unison with other features, as evi- 

 dence of progress in the assumption of the characters of the large, thick-shelled 

 Trimerellids. The specimen figured on Plate II would be unusually large for 

 a species of Lingula. 



Primarily, in reference to the determination of the valves of Lingulasma, we 

 cannot hesitate to regard as the pedicle-valve that which bears the peculiar 

 pedicle-sheath and faint anterior median septum. The brachial valve is 

 then characterized by the strongly elevated septum. Such determination 

 is in harmony with the characters of the respective valves in Trimerella and its 

 closer allies, the stronger septum always appearing in the brachial valve, but it 

 fails to agree, in this respect, with Lingulops, where the septate valve bears 

 accessory evidence of being the pedicle-valve. We are, however, inclined 

 to regard this septum or low ridge in the pedicle-valve of Lingulops as a rem- 

 nant of its inheritance from Lingula, rather than a newly assumed Trimerel- 

 loid character. 



A very remarkable feature in Lingulasma is the enclosed pedicle-sheath. 

 This takes the form of an arching triangular shelf extending from the 

 apex for about one-eighth the length of the valve. Its surface features 

 are precisely those seen in the cardinal area of Trimerella, viz., a broad 



