NOVEMBEU 16, 18S3.] 



SCIENCE. 



653 



series of rocks of the South Valley Hill, these must 

 be the slates referred to, even if ' hydromica slates is 

 a contradiction in terms.' 



While the undersigned certainly does not intend to 

 be a champion for the term'slate' instead of 'schist' 

 for these rooks, good reason for tlie use of that terra 

 lies in the slaty character of many of these hydromi- 

 cas as distinguished from the contorted and schistose 

 character of the micaceous rocks of other regions. 



The writer's use of the expression 'hydromica slate' 

 in describing the Edge Hill and Barren Hill rocks 

 (the 'altered primal slates' of Rogers), is thought 

 preferable to the term ' hydromica schist,' since large 

 portions of that formation are slaty rather than 

 schistose. The greater part of the formation is a 

 slaty sandstone or quartz slate, and, where outcrop- 

 ping in Chester county, is so designated by Dr. Frazer. 

 It might naturally be taken for granted that the 

 ■writer believes, with Dr. Fr.izor, that the hydromica 

 schists and slates of the South Valley Hill of Chester 

 county are about contemporaneous with this quartz 

 slate or Edge Hill rock. 



In order to jirevent future misapprehension, it may 

 here be stated, that the writer has been led to the 

 conclusion that the two formations are distiTict, and 

 that both Professors Rogers and Frazer have con- 

 founded two rock series belonging to different geo- 

 logical horizons, — the one, Cambrian; the other, 

 Silurian. The analogue of the Edge Hill rock is 

 believed to occur in Chester county, on the south 

 side of the hydromicas of the South Valley Hill. 

 The facts leading to this conclusion have been 

 gathered during some extended field-work In Chester 

 county, and will shortly be published. Meanwhile, 

 the remarks upon the primal slates made in the 

 Franklin institute lecture should be understood as 

 referring solely to the Edge Hill rocks proper, and 

 not to tlie South Valley Hill schists or slates, which 

 are but poorly defined in the vicinity of Philadelphia. 

 H. Caevii.l Lewis. 



The specific distinctness of the American and 

 European brine shrimps. 



In Professor Smith's notice of our ' Sfonograph of 

 phyllopod Crustacea,' he states, that, in the portion 

 relating to the above subject, 'there is certainly con- 

 fusion,' and quotes two paragraphs relating to the 

 females alone, and finally remarks, "but diflerences 

 like these in statements of observation betray inex- 

 plicable carelessness." 



After quoting the two paragraphs relating to the 

 femalea alone, it seems to us a careful critic would 

 have also taken pains to have quoted the longer para- 

 graph relating to the males, which directly follows 

 the first paragraph quoted by our critic. To allow 

 the two paragraphs relating to the females to be so 

 widely separated was an oversight on the part of the 

 author, who, however, thought that he had taken a 

 good deal of pains to show the specific distinctness 

 of the American and European species. Two sets of 

 females from different localities, named by different 

 persons, wer6 examined at different times ; and this ex- 

 plains how the two paragraphs became placed too far 

 apart in the author's copy. It would have been bet- 

 ter, of course, if the author had added a few words, 

 and dogniatically stated that the two species were 

 imdoubtedly distinct. He preferred not to do, or 

 omitted to do, this, but gave in consider.ible detail, 

 and in as judicial a way as possible, the facts of the 

 case. At first it was ' diificidl to find good differential 

 characters' between the females, and those found are 

 but slight ones. The females of any of the species of 

 Artemla, Branchinecta, or Branchipus, do not exhibit 



good specific characters; but the males do, as the 

 author attenipteil to show. If the author failed in 

 directness of statement on this subject, or led to any 

 confusion in any one's mind, he sincerely regrets it: 

 on the other hand, he doubts whether there were, 

 in the case, reasons for the charge of 'inexplicable 



The paragraph which Professor Smith would have 

 done well to have quoted is the following one : — 



"Upon comn.nrlng a good mnny mnlcs from Great Salt Lake 

 witb Bcvcral, botli sinlni-d witli carmine and unKtained, received 

 from Cagliail, Sardinia, Ihrongh I'rof. J. McU-od of Ghent, (ho 

 Kniopean A. Enllna is seen to be considerably stouter, Ibc head 

 wider, the ejc-stalks lonjrer and larger, and the eyes Inrjfcr. 

 The frontal billton-llke proccsecs of the first joint of the cinspera 

 are nearly twice as large as in the Amevlenn speeies, and a lltllo 

 more pointed, while the claspers themselves are larger and 

 Bloutei' The legs and sixth endites arc of abonl the same form. 

 The most apparent ditlerencc is in the caudal appendages, or ccr- 

 copods, whleh in A. salina are several times larger than in A. 

 Rracilis, being in the Sardinian specimens nearly three times as 

 long and much larger than in our species. In this ri*pi;et. the 

 genus shows a close nffiliity to Branchinecta. However, in a lot 

 of .\. salina o from Trieste, the cercopods are very mueb shorter 

 than in tlie Sardinian females, and only a little longt'r than in 

 our American specimens. These .appendages do nol diner in the 

 two sexes." , 



A. S. Packard, Jun, 



Bone fish-hooks. 



Recently, while digging In a shell-heap near Xarra- 

 gansett Pier, Rhode'lsland, I found among broken 

 arrow-points, and fmgiuents of bone, pottery, and 

 shells, a nicely worked hcmc-hook, and also the shanks 

 of three other apparently similar hooks; while in a 

 neighboring shell-heap two more fragments were 

 found. 



The perfect hook measures a little more than one 

 inch in length, and a little less than one inch across 

 from the shank to the point, the latter, being nearly 

 as long as the former. The shank Is flattened and 

 notched at the end, forming a sort of head, somewhat 

 similar to the fish-hooks of the present day. This 

 hook, although luuch shorter, resembles a hook from 

 Long Island described and figured by Mr. Charles 0. 

 Abbott on p. 2t)S of his work on Primitive industry. 

 Of this he says, "Objects of this character are ex- 

 ceedingly rare, either as found on the surface, or in 

 shell-heaps. While of so simple a form, bone fish- 

 hooks of this pattern do not appear to be common in 

 any locality in eastern North America." 



Figures are here given of the perfect hook, and the 



