322 
PALAEONTOLOGY OF NEW YORK. 
Atrypa spinosa, vel. A. aspera. 
PLATE LIII A. 
Atrypa spinosa: Hall, Report on Fourth Geological District of Hew York, p. 200, f. 1 and 2. 
Atrypa dumosa: Id. Ib. p. 271, f. 1. 
Compare Terehratulites aspera: Schlothem (Leonhard’s Taschenbuch, pa. 74, tab. 1, f. 7: 1813 ) ; Nach- 
ti-agen Petrefaktenkunde, part 1, p. 363 (95) j part ii, 68, tab. 18, f. 3. Also T. explanata, idem. 
'• Atrypa aspera: Dalman, Uppst. och Beskrif af de i Sverige funne Terebrat., Kongl. Vetens. Acad. 
Handlingar, 1827 : pa. 128, tab. iv, fig. 3. 
“ Terebratula aspera : De France, Diet, liii, p. 164. 1828. 
'• T. reticularis .- Bronn in part, Ind. Palseontologicus, p. 1249. 1848. 
“ Atrypa squamosa : Sowerbt, Trans. Geol. Soc. Lond., 2d series, Yol. v, pi. Ivii, f. 1. 
“ Terebratula (Atrypa) aspera: Phillips, Pal. Fossils of Cornwall, Devon and West Somerset, p. 81, 
pi. xxxiii f. 114. 1841, 
“ Spirigerina reticularis, var. aspera: M'Cot, British Pal.'Fossils, p. 379. 
“ Atrypa reticularis, var. aspera: Davidson, Monograph of British Devonian Brachiopoda, part vi, 
pa. 57, pi. x, f. 5-8. 
Shell robust, suborbicular or oviod; width greater or less than the length; 
radiatingly costate and concentrically lamellose or spinose; hinge-line 
often nearly straight, a little less than the width of the shell. 
Ventral valve depressed-convex, becoming more convex in the upper part; 
nearly flat and often a little concave towards the lateral margins, and 
cardinal extremities depressed or broadly sinuate in front: beak abruptly 
rounded; apex truncate and perforate, closely appressed and overlapping 
the umbo of the opposite valve. 
Dorsal valve convex, becoming gibbous in old shells, flattened or slightly 
concave towards the cardinal angles, regularly curving to the sides and 
baso-lateral margins, and a little elevated in front, but without any dis¬ 
tinct mesial fold. 
Surface marked by strong rounded radiating costse bifurcating at unequal 
intervals, which are much stronger in the middle of the valve, and beeme 
obsolete or appear as gentle undulations towards the cardinal angles. In 
the middle of the valves there are about seven or eight of these costs© 
in the space of half an inch. The shell is also marked by strong concen¬ 
tric lamellae, which are often about a line apart. In perfect shells these 
lamellae, at the crossings of the costse, are often produced into tubular 
