vi Introduction 



and not to those along the west coast of the Peninsula, indicating that this 

 great lagoon was foimerly connected with the Gulf, from which it is now 

 separated by low land. There are descriptions and figures of all mollusks 

 collected by the expedition, as well as those described from the Mazat- 

 lanic faunal area, centering at the mouth of the Gulf. The report will 

 therefore serve as a manual of the mollusks of this region. 



The progress of the dredging work from Cape San Lucas to 

 Monterey, California, is set forth in Part One, pages 431 to 433. The 

 records of soundings made at all dredging stations usually include air, 

 surface, and bottom temperatures, with mud samples, and in some cases 

 specimens of bottom water. Daily records of air and surface temperatures 

 were kept by each watch throughout the voyage. All of the deep-sea 

 soundings plotted on navigational charts of the Lower California region 

 were made during previous voyages of the 'Albatross.' They show all 

 that is known respecting the position of the 1000 and the 2000 fathom 

 lines of depth. The bottom temperatures and other records connected 

 with them are set forth in "Records and Bibliography of the 'Albatross,' ' ; 

 published by the V. S. Bureau of Fisheries. The deep-water soundings 

 made during the voyage of 1911 will be added. 



The comparatively small number of new forms of fishes and inverte- 

 brates dredged from deep water is doubtless due to the abundant dredg- 

 ings previously made by the 'Albatross' both north and south of the 

 Lower California region and during three earlier voyages into the Gulf. 

 The dredgings in general have thrown much light on the subject of the 

 distribution and bathymetric range of deep-sea forms. More than 450 

 specimens of reptiles of 63 species were obtained along the shores of the 

 Peninsula and on islands in the Gulf. Of these, nineteen have been 

 described as new. The total number of species of reptiles known to 

 Lower California and the Gulf islands is 149. The reptilian fauna of the 

 Peninsula has been derived from the north ; that of the islands is related 

 to it except in the case of those near the coast of Sonora. An interesting 

 feature of the collecting work on certain of the Gulf islands was the dis- 

 covery of lizards of large size, one (Ctenosaurus) exceeding thirty inches 

 in length. 



The collection of hundreds of birds and mammals contained several 

 new species, all of which were from islands in the Gulf. The vegetation 

 of Lower California may be roughly divided into that of the northern and 

 central parts related to the flora of the southwestern United States and 

 that of the southern end related in part to the flora of the Mexican main- 

 land, from which it is, however, widely separated by the deep mouth of 



