220 PROCEEDINGS OP THE AMERICAN ACADEMY 



Then the Chazy limestone,, 225 feet thick, contaiiihig a great many 

 of the following fossils: lUcenus arcturus, III. crassicauda ; Asaplnis 

 obtusus, As. inaff/i null's ; Isotelus canalis, Is. giyas ; Ceraurus ; Jlaclu- 

 rea magna, Mud. striat us ; Scalltes angulatus ; Pleurotomariu ; Mar- 

 chisunia ; Bucania or Belleroj^lion ; OrtJioceras rectkinniilutnin, 0. 

 subarculutiim, 0. tenui septum, 0. moniliforme ; Atnjpa ; Ontlds ; Lep- 

 tcena ; Actynocrinus ; Retepora ; Chcstetes, etc. 



Above we have the " Trenton," with the subdivision of the " Birds- 

 eye" and " Black lliver " linu'Stoiie, 3G0 feet thick. The following are 

 very common fossils : Illcenus crassicauda, III. latidorsata ; Calymene 

 multicosta, Cal. senaria ; Isotelus gigas ; Ceraurus ; Phacops ; Asa- 

 phus ; Trinucleus concentricus ; Orthoceras ; Endoceras ; Cyrloceras ; 

 Bellerophon ; Murchisonia ; Plem-otomaria, Holopea ; Modiolopsis ; 

 Tellynomia ; Nucula ; Atrypa ; Spirifer ; Ortliis ; Leptceua ; CItcete- 

 tes, etc. 



The " Utica slate," at Rouse's Point and Alburgh peninsula, with 

 TliriartJirus {Calymene) Beckii and Graptulil/ius pristis most abun- 

 dant, has a thickness of about 105 feet. 



This section is the most complete that we have in America ; even 

 that of Nevada recently found at Eureka by Mr. Charles D. Walcott 

 is less satisfactory for the Champlain series and the Potsdam sand- 

 stone. But there are two "gaps," to which I invite attention by try- 

 ing to fill them without going far from Lake Charai)lain. These 

 "gaps" are in the upper part of the Tuconic, and are owing to the 

 two " breaks " with discordance which took place before and after the 

 deposit of the Potsdam sandstone. 



But first I will give an extract from the last letter which I have 

 received from the promoter of my researches on the Taconic system, 

 my most regretted friend, Barrande. 



" Pragdb, 10 Mars, 1882. 

 "MON CHER INIONSIEUR MaRCOU. 



". . . . Depuis que j'ai vec^n, en Avril, 1881, votre beau nit'moire 

 Snr les Colonies dans les Poc/ies Taconiques dcs Bords du Lac Cham- 

 plain, il est reste sur ma table de travail. A diverses reprises je I'ai 

 etudie pour bien apprecier vos observations et en reudre compte dans 

 ma Defense des Colonies VI., en pre[)aration. 



*• II m'est agrcable de reconnaitre, que vos nouveaux documents sout 

 bien supcrieurs a ceux que vous avez d'abord j)ubliees et meritent 

 toute consideration. La multitude de mcs occupations uigentes ne 

 me pprmet pas aujourd'hui d'eutrer dans la discussion des faits eu 

 question. 



