80 I LR (GQUSSLIB M- 
as, besides other reasons, it lacks any very evident graptolitic texture or struc- 
ture and has 24-26 oblique ribs as compared with (from measurements on 
Hall’s figures) some 35-40 for G. venosus. 
RETEOGRAPTUS HALL, 1859. 
Pal. N. Y., IIl., p. 518. Type &. tentaculatus (Hall). 
A specimen of &. ¢entaculatus in the American Museum of Natural His- 
tory, New York City, exhibits practically the same type of structure as is seen 
in PR. geznttzianus from the Lower Dicellograpsus zone. 1 have no doubt that 
they are congeneric. Lapworth has, however, referred PR. geznztzzanus to his 
Clathrograptus* (founded on C. cunetformis Lapw.). If C. cunetformis be, 
indeed, congeneric with &. gednztz¢anus, the genus Clathrograptus must be 
suppressed. 
Reteograptus geinttzianus Hall, 1859. 
Reteograptus geinitzianus, Pal. N. Y., Ill., p. 518, with fig.; Reteograptus 
barrandi Hall, 1860, 13th Rep. N. Y. St. Cab. Nat. Hist., pp. 61-62, 
with fig.; Clathrograptus geinitzianus Lapworth, 1880, Ann. and 
Mag. Nat. Hist., V., p. 22. 
Some particularly favorable preservation-conditions occur among the 
Stockport specimens. They permit the following description: The polypary 
in this species is parallel-sided blunt-fusiform, and consists of skeleton and 
periderm. The skeleton shows, at and imbedded in its base a body appar- 
ently a sicula, flanked on either side by a spine which is directed obliquely 
upward. Two virgulas are present, each zigzagged in the basal expanding 
portion of the polypary, straight in the middle (parallel-sided) portion, and (?) 
again zigzagged in the upper contracting part. From the convex angles of 
the zigzagged, and at intervals from the straight portion of the virgula, 
a parietal ledge? runs in each lateral wall to the ventral margin, where it 
undergoes an abrupt deflection downward to the parietal ledge of the theca 
next below, to which it appears to connect just before (Zz. ¢., at a point on the 
lateral surface just within the ventral margin) that ledge reaches its point of 
downward deflection. At the latter point a mouth ledge connects the parietal 
ledge with its fellow on the opposite side. These three chitinous threads (the 
horizontal limb of the parietal ledge, the vertical limb of the same and the 
mouth ledge), all meet at the point of deflection with rounded edges, and 
together form the rim of the mouth opening, which is thus somewhat squarish 
or slightly trapezoidal. I have seen nothing corresponding to the inner 
cross-ledges and the material furnishes no data for an opinion pro or con as 
to the existence of any interthecal partition planes. 
Geol. Mag., 1873, X., p. 559. 
27 here follow the nomenclature of Holm (Bihang til kongl. Sv. Vet.-Akad. 
Handl., 1890, XVI., No. 7). 
