214 MRS. JA.XE LONGSTAFF ON [May 1909, 



It is somewhat remarkable that the most deeply sinuated species 

 of Loxonema, such as L. sinuosum (Sow.) and L. intumescens, Lindstr., 

 as well as the only described species of Sinuspira, Perner, and the 

 spirally striated subgenus Rhabdostropha, occur in the higher 

 Proterozoic strata. As these forms seem to come nearest in 

 appearance to the Murchisoniidae, we might have expected them to 

 occur earlier. 



Range. — Species have been referred to this genus from the 

 Ordovician up to the Lias ; but most of those placed here subsequent 

 to the Carboniferous and also some occurring in that formation do 

 not belong to the genus sensu stricto. 



The British Proterozoic species range from the Bala up to and 

 throughout the Ludlow Formation. Besides the genotype L. sinuo- 

 sum (Sow.), there have been described four other species, namely, 

 L. elegans, M'Coy, from the Lower Ludlow, L. striatissimum, Peed, 

 from the Upper Bala, L. grindrodi, Don., from the Lower Ludlow, 

 and L. pseuclofasciatum, Don., from the Wenlock Limestone. The 

 two latter do not belong to Loxonema s. str., but have been placed 

 in the subgenus Rhabdostropha, Don. The holotype of L. elegans, 

 M'Coy, is in the Sedgwick Museum, Cambridge, and is too badly 

 preserved to make out the structure sufficiently to refer any other 

 shell to the species. In addition to these, I am here describing as 

 new to Britain seven species and one variety of Loxonema s. str., 

 one species of Rhabdostropha, and two species probably referable to 

 Stylonema. Further, I am giving the description of a new species 

 of Hormotoma from the Llandeilo Formation, as it is the oldest 

 undoubted representative of the genus at present known to me in 

 Britain. 



Lindstrom records six Proterozoic species from Sweden, namely, 

 L. dalecarlicum, Lindstr., from the Leptcena - Limestone, and 

 L. sinuosum (Sow.), L. attenuatum, Lindstr., L. intumescens, Lindstr., 

 L. strangulatum, Lindstr., and L. (?) fasciatum, Lindstr., from the 

 Silurian. Through the kindness of Prof. Gerhard Holm I have been 

 enabled to compare the Gothlandic with the British forms, and I 

 find that L. intumescens is the only species that appears to be repre- 

 sented in Britain. The L. sinuosum of Lindstrom is quite distinct from 

 that of Sowerby — the whorls being more excavated above and more 

 convex below, and the sinus being situated lower down ; it also 

 occurs on a lower horizon. It must, therefore, be regarded as a new 

 species, for which I suggest the name L. lindstrbmii. L. attenu- 

 atum has a narrow and faintly limited band, and seems closely allied 

 to the species referred by Dr. Perner to the subgenus Goniospira, 

 Donald 1 (Donaldiella, Cossmann) 2 , more especially to D. gracillima, 

 (Barr.). This shell has not so prominent a band as the type, 

 D. filosa, Don. Loxonema (?) fasciatum probably belongs to the 

 genus Sinuspira, Perner. 



The family is more richly represented in Bohemia, where 

 Dr. Perner records twenty-five species from the Silurian, eight 



1 Quart. Journ. Geol. Soc. vol. lviii (1902) p. 328. 



2 ' Revue de Paleozoologie ' vol. vii (1903) p. 68. 



