Exodermis an outermost layer of thickened or suberized cortical cells that sometimes replaces the epidermal layer in the older parts of roots if the epidermal cells have died 外皮层：薄的或木栓化的皮层细胞的最外层。如果根的较老部分表皮细胞死亡，它通常取而代之。
2.
The thirty - four species of the sea urchins belong to 7 order , 17 families and 28 genera . the following is the name list , those with an asterisk are the species recorded for the first time in china . order cidaroida family cidaridae * goniocidaris biserialis ( d6derlein ) * stylocidaris bracteata ( a . agassiz ) * stylocidaris ryukyuensis shigei * stereocidaris indica philippinensis mortensen * rhopalocidaris gracilis doderlein order lepidocentroida family echinothuridae * phormosoma bursarium ( a . agassiz ) araeosoma owstoni mortensen asthenosoma ijimai yoshiwara order stirodonta family phymosomatidae glyptocidaris crenularis a . agassiz family arbaciidae * coelopleurus maculata a . agassiz et h . l . clark * coelopleurus undulatus mortensen order aulodonta family diadematidae chaetodiademajaponicum mortensen family pedinidae * caenopedina mirabilis ( d6derlein ) order camarodonta family temnopledridae temnopleurus hardwickii ( gray ) temnopleurus toreumaticus ( leske ) temnopleurus reevesii ( gray ) temnopleurus apodus ( a . agassiz et h . l . clark ) temnotrema sculptum ( a . agassiz ) temnotrema reticulatum mortensen * microcyphus olivaceus ( d6derlein ) * prionechinus forbesianus ( a . agassiz ) family strongylocentrotidae strongylocentrotus nudus ( a . agassiz ) hemicentrotus pulcherrimus ( a . agassiz ) family echinometridae anthocidaris crassispina ( a . agassiz ) order clypeasteroida family clypeasteridae clypeaster virescens doderlein family laganidae * peronellapellucida d5derlein family scutellidae * scaphechinus mirabilis a . agassiz sinaechinocyamus planus liao family fibulariidae fibularia acuta yoshiwara order spatangoida family loveniidae - lovenia triforis koehler echinocardium cordatum ( pennant ) family schizasteridae schizaster lacunosus ( linnaeus ) family brissidae * gymnopataqus magnus ( a . agassiz & h . l . clark ) family spatangidae * spatangus luetkeni a . agassiz among the species reported , the following species call for notes or simple descriptions 本文根据th . mortensen ( 1928 - 1955 )海胆专著( amonographoftheechinoidea )中的主要分类依据，将海胆纲分为8个目： 1 )头帕目( cidaroidea )有齿器，围肛部在顶系内，围口部有步带板和间步带板，大棘很大，有外皮层，无球棘； 2 )鳞棘目( lepidocentroida )有齿器，围肛部在顶系内，围口部仅有步带板，大棘不很大，无外皮层，有球棘； 3 )脊齿目( stirodonta )有齿器，围肛部在顶系内，齿器的齿有脊，桡骨片在齿上方不相接，颚孔开放； 4 )管齿目( aulodonta )齿器的齿无脊，围肛部在顶系内； 5 )拱齿目( camarodonta )有齿器，围肛部在顶系内，齿器的齿有脊，桡骨片在齿上方相接，颚孔封闭； 6 )全雕目( holectypoida )有齿器，但不发达或完全被吸收，围肛部在顶系外，步带不形成瓣状和叶鳃； 7 ) ?形目( clypeasteroida )齿器发达，围肛部在顶系外，步带形成瓣状，无叶鳃； 8 )猬团目( spatangoida )无齿器，围肛部在顶系外，叶鳃发达，步带形成瓣状。
