Occasional Papers Ol THI-: CALIFORNIA ACADEMY OF SCIENCES VII SAN FRANCISCO 1900 PUBLICATION C< )MM ITT EE. CHARLES H. GILLERT, Chairman. WILLIAM E. RTITER, G. P. RIXFOKL, anITORS (>i< /A n)/. ( X;ICAL PL :I:LICA TH\\S. CHARLES H. GILBERT. W'ILLIA.M E. R TITER. SYNOPSIS California Stalk-Eyed Crustacea BY SAMLKL j. IIoL,MES /ss//t'i/ June /j, igoo SAX FRANCISCO CALIFORNIA ACADEMY OF SCIENCES 1900 PRINTED FROM THJ; HEXDRIE PUBLICATION FUND. PREFACE. The aim of the present paper is to give descriptions of the species of Stalk-eyed Crustacea which are found on the west coast of the United States. For the benefit of students of natural history, who have at present few readily accessible means of identifying the invertebrate animals of this coast, definitions of genera and higher divisions have been inserted, and a description given, in the Introduction, of those parts of the structure of the Decapod Crustacea which are most used for the purpose of classification. The endeavor has been made to enable those who have not previously studied the Crustacea to determine the specific names of the forms here described. The rules of nomenclature of the American Ornithologists' Union have been followed, except in case of the canon, not insisted on by the framers of the code, that specific names derived from the names of persons be written with a small letter. Localities from which I have examined spec­ imens have usually been indicated by the note of exclamation, !. The larger portion of this paper was completed at the University of California in 1895, but it has received some additions and considerable revision since that date. I wish to express my indebtedness to Prof. Wm. E. Ritter of the University of California for many favors in connection with my work, and to Dr. H. P. Johnson and Dr. F. W. Bancroft for several valuable specimens and for assistance in many other ways. Through the kindness of Dr. Gustav Eisen I have had 6 PREFACE. the privilege of studying the collections of Crustacea in the California Academy of Sciences. The examination of Mr. Lockington's type specimens, many of which are in the possession of the Academy, has made it possible to straighten out some questions which otherwise would scarcely have been capable of solution. To Mr. Rivers and Mr. Harford, formerly of the University of Cali­ fornia, I am indebted for the privilege of studying the collections in the University museum. From Miss Mary J. Rathbun and Dr. James E. Benedict of the U. S. National Museum much valuable aid has been received which is gratefully acknowledged. S. J. HOLMES. UNIVERSITY OF MICHIGAN, Ann Arbor, Mich. January 20, 1900. SYNOPSIS OF CALIFORNIA STALK-EYED CRUSTACEA. BY SAMUEL J. HOLMES. INTRODUCTION. THE Crustacea are commonly divided into two princi­ pal groups, the Malacostraca and the Entomostraca, although the primary divisions of the latter group may well be, as they often are, considered coordinate with the former. There is such great diversity of form among the Entomostraca that the group is scarcely definable except by negative characters. The number of segments composing the body is very variable and the openings of the genital ducts do not occur in the same segment in all the members of the group. There is no masticatory stomach and corresponding append­ ages are modified in most diverse ways in different orders. The Malacostraca, on the other hand, while they include a great variety of forms, constitute a well defined subclass. Except in cases in which it is quite evident that certain segments are fused or lost, the body is composed of twenty (or in •Nebalia of twenty-one) segments. The typical number of appendages is nine­ teen. There is a pair of compound lateral eyes, and the stomach, except in a few parasitic species, is masticatory. The genital ducts of the male open on the last thoracic segment; those of the female on the antepenultimate one. The head is typically composed of five segments [7] 8 CALIFORNIA ACADEMY OF SCIENCES. and the thorax of eight, some or all of which may fuse with the head forming a more or less complete cephalo- thorax. The abdomen is sharply marked off from the thorax and consists of seven (in Xebalia of eight) seg­ ments, all of which, except the last, the telson, may bear articulated appendages. The Malacostraca may be divided as follows:— Body composed of 21 segments and furnished with a bivalve shell. Leploslraca. Body composed of 20 segments and not furnished with a well defined carapace. Eyes sessile Arlhroxlraca. Body composed of 20 segments and furnished with a well developed carapace which is never bivalved Thoracostraca. SYNOPSIS OF THE THORACOSTRACA. Eyes sessile Cumacea. Eyes stalked. Carapace rather small, not covering all of the thoracic segments. The thoracic feet dissimilar, the anterior ones devoid of exopods. Stomatoj>oda. Carapace covering some or all of the thorax but not joined to the posterior segments. Thoracic feet usually similar, biramous. Schizopoda. Carapace covering and joined to all of the thoracic segments. The three anterior thoracic feet generally biramous and modified into mouth-parts Decapoda. As it is with the Decapoda that we are here mainly con­ cerned, those parts of the structure of these animals which are most used for the purpose of classification will be briefly described. The exoskeleton of a Decapod crustacean may be considered as a series of rings, each of which, with the exception of the last, is typically furnished with a pair of articulated appendages. These rings and their appendages are modified in various ways in different regions of the body in relation to the different functions they are called upon to perform. CALIFORNIA STALK-EYED CRUSTACEA. 9 The segments in some parts become fused together so completely that they manifest no external signs of metamerism except the appendages they carry. The live segments forming the head are usually thus indis- tinguishably fused. The eight following segments, with the rare exception of the last one, are fused together and with the head, forming the cephalothorax; but the sutures between the rings are, in this case, generally visible on the ventral, or sternal surface and at the sides. The abdomen is, in all cases, clearly marked off from the thorax, and is typically composed of seven segments. The number of joints may, however, be secondarily reduced by the concrescence or disappear­ ance of some of the rings. The Gara-pace.—The carapace of the Decapod Crustacea is considered to be a fold of the dorsal integument of one or more of the cephalic segments which extends backward over, and fuses with the dorsal portion of all of the thoracic segments and is produced downwards at the sides over the gills. The form of the carapace commonly found in the Macroura is shown in the fol­ lowing cut:— Fig 1.—Macrouran Carapace, a. s, antennal spine; b. r, branchial region; c. g, cervical groove; h. s, hepatic spine; r, rostrum; n. o. s, suborbital spine; s. s, supra­ orbital spine. 10 CALIFORNIA ACADEMY OF SCIENCES. The typical Macrouran carapace is elongated, and the anterior end is produced into a rostrum. The anterior region of the carapace is often furnished with teeth or spines which occur in the following positions: the supra­ orbital spine, or spines, above the orbit; the suborbital spine on the anterior margin of the carapace below the orbit; the antennal spine below the last and behind the base of the antenna; the hepatic spine on the he­ patic region. Any or all of these spines may be present or absent. There is generally visible a groove, known as the cervical groove, which extends downwards and forwards from the dorsal surface of the carapace, mark­ ing the line of union of the head and thorax. The dorsal surface in front of this groove is termed the gastric region, the hepatic regions lying at the sides; immediately behind the gastric region is the cardiac, while the intestinal region lies behind the latter at the posterior end of the carapace; the sides of the carapace behind the cervical groove are known as the branchial regions, since they form a covering for the branchiae, or gills. In the Brachyura the carapace is wide and generally flattened, and the rostrum is small or absent. The regions are generally separated from each other by sulci, or grooves, and there are usually more regions marked out than in the Macroura. The cervical groove is usually visible and divides the gastric and hepatic from the cardiac and branchial regions. On the sides of the carapace below the lateral margins there are (1), the pterygostomian region on either side of the mouth area and (2), the sub-branchial regions below the branchial areas. The names of the regions which appear on the dorsal surface may be obtained from fig. 2. The dis­ tinctness of these areas is subject to great variation in CALIFORNIA STALK-EYED CRUSTACEA. 11 different forms. In some cases the outlines of all the regions are very clear, while in others they may be entirely obliterated. Other areas are sometimes given names but they are of little importance. Fig. 2.—Carapace of a crab. 3.—Mandible of a crayfish. 4.—First maxilla. 5.— Second maxilla. 6.—Third maxilliped. 6, basipodite; b. r, branchial region; c, coxo- podite; c. g, cervical groove; cp, carpus; c. r, cardiac region; d, dactyl; en, endopodite; ep, epipodite; ex, exopodite; h. r, hepatic region; i, ischium; i.r, intestinal region; m, merus; in. r, mesogastric region; p, palp; p. g, protogastric areas; pr, propodus ; r, rostrum; u, urogastric area.