RANDOM NOTES ON NATURAL HISTORY. 



31 



color, with dark brown bands arranged 

 obliquely across the whorls. Aperture when 

 viewed from below nearh' circular, lip simple 

 and sharp, whorls six. The base of the 

 shell is lighter in color than the upper sur- 

 face. Diameter one inch." 



Tliese shells arc found all over our state 

 on decaying stumps and logs, but never of 

 size given by ]\Iorse. Even at Lime Rock 

 in Smithfield, where we find them crawling 

 over the broken masses of limestone, they 

 never exceed three quarters of an inch and 

 rare 13^ attain that size. The difference in 

 size of our alternatas and those from the 

 west is even more striking than in the case 

 of Mesodon albolabris. The shells of this 

 species are carinate while 3'oung, that is, 

 the}" have a sharp line running around the 

 centre of the shell, dividing the upper from 

 the lower surface. This line disappears at 

 maturity, forming a well rounded surface 

 and a circular aperture. Generally several 

 specimens are found together, thus differ- 

 ing in their habits from the preceding 

 species, which are usually solitary. 



88. Patui.a (Discus) Striatella, Anth. 

 Syns. : 



Helix striatella, Anth., Gld., Binn., Ad., 

 Chem., Pfr., Reeve, Morse. 



Helix ruderata, Adams, non Studer. 



Anguispira striatella, Tryon. 



Patula striatella, Morse. 



In 1817 Mr. Say described a shell which 

 he named Helix perspectiva. The species 

 now under consideration was for many ^ears 

 confounded with Sa^^'s perspectiva. 



Several gentlemen in Ohio, where both 

 species abound, had observed the difference 

 in the two shells sometime previous to 1840, 

 when Mr. John G. Anthon}' published a 

 description of the new species under the 

 name of Helix striatella, in the Joiirn. Bost. 

 Soc. Nat. Hist., iii.. 278. Helix perspec- 

 tiva is not found in New England, but stri- 

 atella is very common here and throughout 

 the United States north of Virginia, extend- 

 ing into Canada and British America. 



It is about one quarter of an inch in di- 

 ameter, of a uniform reddish horn color, 

 depressed, convex, almost discoidal ; whorls 

 four, flattened above and rounded below, 

 with sharp elevated lines of growth, not 

 parallel with the whorls as in lineata, but 

 across them: suture distinct; lip simple 

 and thin ; umbilicus broad and deep, ren- 



dering the base of the shell cup shaped. It 

 is found about old stumps and under the 

 bark of decaying logs ; also under leaves 

 near the margins of ponds. 



89. Patula (Pseudohvalina) ExKiUA, 

 Stimp. 



Syns. : 



Helix exigua, Stimp., Gld., Binn., Morse. 

 " anuulata. Case., Pfr. 

 " striatella junior, Gld. 



Pseudolu'alina exigua, Morse, Tryon. 



This shell was described by Dr. William 

 Stimpson, as Helix exigua, in the Proc. 

 Bost. Soc. Nat. Hist., in.. 175, 1850. 

 The genus Pseudohyalinn was founded by 

 Morse in 1864. In papers on the " Con- 

 cholog}' of Rhode Island" prepared for the 

 Providence Franklin Society in 1871, b}' the 

 writer, it was described as a sub-genus of 

 H\'alinia. Tryon in Structural and Syste- 

 matic Conchology, 1884, places it under 

 Patula as a sub-genus of Helix. Tr3on's 

 Manual of Concholor/y, 1886, classifies it 

 thus : Famil}' Zonitidae, Genus Zonites, 

 Montfort, 1810. Sub-genus Striatura, 

 Morse, 1864. Section Pseudohyalina, 

 Morse, 1864. 



" Shell broadly umbilicated, depressed, 

 pellucid, greenish horn color, marked with 

 delicate revolving lines, and distant, longi- 

 tudinal ribs, obliquely decussating the in- 

 cremental stritie ; whorls three and a half, 

 aperture oblique, transversely rounded ; lip 

 simple, acute." 



It is quite common in Maine and in Can- 

 ada ; more sparingly in the other northern 

 tier of states to Wisconsin, and ma}' be 

 considered as a rare shell in Rhode Island. 

 Its umbilicus is wide but shallow, showing 

 all the volutions. Diameter one-tenth of 

 an inch. Under the microscope with a one 

 inch objective, it is a most beautiful object ; 

 in fact, the longitudinal ribs and the deli- 

 cate revolving lines between them cannot 

 be seen unless the shell be magnified some- 

 what ; a common pocket lens, however, will 

 bring out the characteristic marks which 

 distinguish this species from any other of 

 our land shells. 



(To be continued.) 



The new Union Check-List is now read}' 

 See advertisement. 



