Vol. 58.] REFERRED TO MURCHISONIA AND PLEUROTOMARIA. 310 
Bellerophontide, and Murchisoniide. Since then,’ he has removed 
the Murchisoniide and the Bellerophontide from it. He differs 
from Ulrich & Scofield in separating the elongated forms re- 
ferred to Murchisonia from the Pleurotomariide, causing them to 
constitute a distinct family. He considers that the Kuomphal- 
opteride also constitute a separate family, instead of regarding 
them as a genus of the Raphistomide ; and he excludes moreover 
the Trocho-Turbinide from this suborder, placing them in a different 
suborder, which he calls Trochomorphi. Prof. Koken, how- 
ever, agrees with Ulrich & Scofield in regarding the sinus as 
the earlier structure, and he considers that the slit has gradually 
developed from it. 
It is not quite clear whether Ulrich & Scofield believe the slit 
to have developed from the sinus or not. On p. 948 (op. gam cit.) 
they state that the slit 
‘seems to be a later phase in the evolution of the majority of the lines of 
development that can be traced from the Lower Silurian into subsequent 
periods.’ 
On p. 949 they write that in 
‘ Hormotoma we have good evidence showing a gradual development of the 
slit. In all the Lower and Upper Silurian species of this genus a deep 
V-shaped apertural notch is present, but no slit. In, however, what we con- 
sider to be Devonian representatives of the same type of shell (e. g. Murchisonia 
desiderata and Maza, Hall) we observe that the bottom of the notch is prolonged 
into’a short slit, but the backward sweep of the edges of the outer lip forming the 
notch is quite as pronounced asin the earlier species which have no slit. From 
this and the preceding case, therefore, it is evident that the slit did not take the 
place of a deep notch, but that it is really an additional and distinct feature.’ 
Lower down on the same page they say, 
‘It is interesting to note that, as far as we now know, the slit, which further- 
more seems to have been developed almost suddenly, is longer in the earliest 
species known to possess one than in any of the later Palxozoic forms.’ 
- Though Ulrich & Scofield trace the earliest appearance of repre- 
sentatives of the family Pleurotomariide (as constituted by them) 
in America, they do not throw any light on the first appearance of 
true Murchisonia, for they state? that strictly speaking they do not 
consider that the genus is represented in America. Unfortunately 
Prof. Koken does not distinguish clearly between the elongated 
forms having a slit and those with merely a sinus, but he refers all 
to his family Murchisoniidew. He considers it probable that the 
Murchisoniide and Loxonematide have originated from the same 
stock,’ and also that the Turritelle+ may have developed from them 
later on. If this were correct with regard to the Turritelle, we 
should expect them to yield some decided evidence of a very primitive 
origin, but this is not the case, as the recent researches of W. B. 
Randles clearly show. It remains to be proved whether the recent 
forms with a sinus, hitherto referred to Turritella and Murchisonia 
1 Neues Jahrb. 1898, vol. i, p. 12. 
* Final Rep. Geol. & Nat. Hist. Surv. Minn. vol. iii, pt. ii (1897) p. 960. 
3 Jahrb. d. k.-k. geol. Reichsanst. vol. xlvi (1896) p. 62. 
* ‘Die Gastrop. des Balt. Untersilurs’ Bull. Acad. Imp. Sci. St. Petersb. 
ser. 5, vol. vii (1897) p. 201. 
