SINUITOPSIS. 17 



16. Sinuites sp. 



Certain specimens (^), from the Middle Bala of the Teirw River, in the 

 Sedgwick Museum, do not seem strictly referable to S. blluhatu.s (though they were 

 thus labelled by Salter), or to any of the above described species, but their 

 poor state of preservation and the broken apertural margins do not allow of a 

 specific diagnosis. The umbilicus is situated below the middle of the shell as in 

 S. haldatclilensu, and the shell has similarly a more sharply arched and parabolic 

 dorsum than 8. hilohatus. From both of these it differs by the possession of a 

 strong transverse internal thickening continuous from the umbilicus on one side to 

 that on the other side, gently arched forward laterally and curved back in a broad, 

 shallow, rounded lobe on the dorsum ; it is situated at about half the lencrth of the 

 outer whorl, and there are traces of other weaker internal thickenings on the sides 

 of this whorl, but they are not continued across the dorsum between it and the 

 mouth. We may perhaps compare it with 8. suhcompressus (Ulrich)," 8. ohesus 

 (Ulrich),^ and 8. strangulatus (Barrande).* 



Dimensions. — Height, about 30 mm. 



Horizon. — Middle Bala Beds. 



Localitij. — Teirw River, S. of Llangollen. 



Genns SINUITOPSIS, Perner. 



Generic Characters. — Shell con.pletely symmetrical, discoidal, of 2 — 3 whorls, 

 which touch and partly embrace one another. Dorsum of last whorl rounded, but 

 in internal casts carinated or sharply ridged. Transverse section of last whorl 

 subquadrangular. Umbilicus not very deep, partly covered by a callosity. 

 Mouth not much enlarged, with shallow rounded sinus. No slit-band. Test 

 thick, specially thickened in several places. 



This genus^ does not seem to rest on a very firm foundation, and it combines the 

 features of several pre-established ones. Perner himself says that it represents 

 a transitional form of 8i7iuites, connected on one side with Gyrtolites, and on the 

 other with Temnodisciis. The one Girvan form here described under this generic 

 name may almost equally well be referred to Temnodiscus, if we follow Perner in 



1 TJlrich and Scofield, op. cit., p. 870, pi. Ixiii, figs. 28—30. 



2 Ihid., p. 873, pi. Ixiii, figs. 40—44. 

 ^ Ibid., p. 874, pi. Ixiii, figs. 45—47. 



* Perner, op. cit., p. 159, pi. Ixxxvii, figs. 12 — 14. 

 5 Jbid., p. 67. 



